Obviously something can be sub-optimal or poor, minimal, bad or terrible... But is there a word that means the exact opposite, the antonym, of optimal?

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    Hi mystery downvoter, could you please explain why you've downvoted me so I know how I can improve my question?
    – CLockeWork
    Commented Jun 17, 2014 at 8:36
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    afaik, the majority of uses of 'sub-optimal' are (sarcastic) understatement, making the word carry the meaning you're looking for.
    – Bakabaka
    Commented Jun 17, 2014 at 9:54
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    Bollobas, Bela. Modern Graph Theory. 1998., "Optimal and Pessimal Orderings of Steiner Triple Systems in Disk Arrays" en.wiktionary.org/wiki/pessimal & books.google.ca/…
    – Kris
    Commented Jun 17, 2014 at 10:33
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    I feel like worst may not be a bad choice. You know, if you don't want to say megatronic.
    – Magus
    Commented Jun 17, 2014 at 14:50
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    I agree that worst is probably a good choice, especially with its much higher extent of common usage. Optimal means something like "Most suited to the task/situation", therefore the word desired (and the accepted answer, pessimal hits this on the head) must be one which means "least suited to the task/situation". Worst doesn't mean exactly that, but it's close enough to be suitable, and much more common.
    – asfallows
    Commented Jun 17, 2014 at 15:44

10 Answers 10


Taking the classical approach, optimal derives from optimus, the Latin superlative to bonus, meaning good.

Looking at the Latin for bad, that is malus.

bonus -> melior -> optimus
malus -> peior -> pessimus

So analogous to optimus becoming optimal, pessimus would become pessimal.

All that said, I have never heard that word used.

We do use plenty of the forms of Latin good and bad, as in ameliorate, pejorative, optimal, optimist and pessimist. However, pessimal never seems to have made it far in the popularity contests - it did get into the dictionaries though!

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    As a fun fact, pésimo (the literal translation of "pessimal" in Spanish) has widespread usage in the language. Great question and even better answer!
    – AeroCross
    Commented Jun 17, 2014 at 10:35
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    It's a commonly used word in engineering.
    – Mitch
    Commented Jun 17, 2014 at 10:54
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    In Maths and Computer Science too
    – Slicedpan
    Commented Jun 17, 2014 at 11:44
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    @CLockeWork It's probably not in common use because it's hard to say that something is in it's worst state or has the least capability. It's easy to say that it's bad, but the worst? Given the words are by nature more technical terms (and thus wouldn't be used generally as an overstatement), it wouldn't oft be used.
    – Doc
    Commented Jun 17, 2014 at 13:42
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    FWIW - Terry Pratchett used Pessimal to name one of his Discworld characters.
    – Peter Wone
    Commented Jun 18, 2014 at 9:59

Since pessimal is correct in the worst possible way, I would look more carefully at the specific usage. One common antonym in discussions of algorithms that would probably fit many usages is "worst-case." You will often see optimal and worst-case performance contrasted as well as optimal (aka best-case) scenarios and worst-case scenarios.

  • A very good point mmdanziger :)
    – CLockeWork
    Commented Jun 19, 2014 at 15:43

I think you simply had not understood the meaning of "optimal". It's just a elevated synonym of "best". (from Latin "optimus") And its antonym is simply "worst".

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    It's ironic that the more high-falutin' word "pessimal" gets the votes, when here is a plain old word that is the right answer :) Commented Jun 20, 2014 at 12:27

exact opposite of "optimal" is "non-optimal"

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    Thanks for your input indian, but Non-optimal means not optimal, even a tiny point off of optimal can be said to be non-optimal so non-optimal isn't the opposite of optimal
    – CLockeWork
    Commented Jun 18, 2014 at 12:11
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    @CLockeWork: While I don't believe this is a good answer, I would argue that it isn't always clear what opposite really means. There are many cases where "even a tiny point off optimal" is completely unacceptable and utterly wrong, and being two or three or a million points off optimal is no worse.
    – John Y
    Commented Jun 20, 2014 at 13:01
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    A good point @JohnY, while I wanted be clear that I was looking for the technical antonym of the word, in an emotional context there's a whiole lot of wiggle room there.
    – CLockeWork
    Commented Jun 20, 2014 at 15:00


google the word. it should fit your need.

  • Am I crazy or didn't this answer occur before the one with 76 votes that comes to the same conclusion? I realize the other answer is more thorough, but still...
    – TTT
    Commented Jun 19, 2014 at 21:50
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    @TTT if that's the case, it just shows how a complete, well explained answer is rewarded for its effects. And vickvace, I wish you would at least capitalize the first letter in a sentence, this is ELU not Yahoo.
    – Mari-Lou A
    Commented Jun 20, 2014 at 0:23
  • @Mari-LouA, that's exactly it; if multiple answers are the same then the most complete and thorough one gets my vote :)
    – CLockeWork
    Commented Jun 20, 2014 at 8:03

It may not always be applicable, but "pathological" may be a good choice.

If something is optimal, it is a/the best combination of all relevant factors.

If something is pathological, it is a/the worst combination of all relevant factors.

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    Pathological doesn't mean that. Commented Jun 17, 2014 at 17:02
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    yes it does, in hacker jargon.
    – Phil Frost
    Commented Jun 17, 2014 at 20:45
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    @PhilFrost I don't think so - all three variants allow that there are multiple pathological cases, each very bad, but not exactly in the same way. The "un-optimal" case is only one, or at least multiple cases that are exactly as bad as the others - that's the essence. Commented Jun 18, 2014 at 3:54
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    I intended it in the Mathematical sense en.wikipedia.org/wiki/Pathological_(mathematics) although the jargon file pretty much matches that: something which goes completely against what you were trying to achieve, whilst still obeying all the conditions you imposed.
    – Warbo
    Commented Jun 18, 2014 at 11:11
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    I agree with @DJClayworth, it doesn't mean that even in mathematics. There can be many different pathological cases; none of them may be the worst possible one. Commented Jun 18, 2014 at 16:06

If you trust on WordNet (http://wordnetweb.princeton.edu/):

optimum, optimal (most desirable possible under a restriction expressed or implied)

antonym: worst [Indirect via best] ((superlative of `bad') most wanting in quality or value or condition) "the worst player on the team"; "the worst weather of the year"


Generally this requires a sentence, because as tribal monkeys we like to dwell on bad situations and defeats.

It was the very abject point of hopelessness

things were as bad as they could ever be

he had given up all hope

But here are some words you could try; Horrid, abject, hopeless, worst, dreadful, awful, woebegone, abysmal, dire.

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    All the suggestions are in the spirit of the request correct, but are not precise and seemingly subjective (which is, of course, my subjective opinion to be precise ;).
    – hauron
    Commented Jun 17, 2014 at 11:57

Around here (IT department) the phrase the Murphy way of doing things is commonly used as opposite of the optimal way of doing things.

Derived obviously from "Murphy's Law":
Anything that can go wrong, will go wrong, at the worst possible moment, causing maximum damage.

May not be generally suitable, but for us it works.

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    That's not Murphy's Law. Murphy's Law is that people will do the wrong thing, at least some of the time, if given the opportunity. It's a design principle (don't give them the opportunity).
    – Jon Hanna
    Commented Jun 17, 2014 at 15:56
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    @JonHanna: My memory, and wikipedia, disagree with you: en.wikipedia.org/wiki/Murphy's_law Commented Jun 17, 2014 at 18:57
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    @MooingDuck that link agrees with me.
    – Jon Hanna
    Commented Jun 17, 2014 at 21:17
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    First sentence on the page uses "Anything that can go wrong will go wrong.". The examples in the History section are "everything goes wrong at sea with regard to machinery" "All results will happen with enough experiments" "Everything goes wrong when performing" "Everything goes wrong with mountaineering" "Everything goes wrong as a law of thermodynamics", the only example referring to a person making mistakes that I see is the last "He will make every mistake". Do you interpret the others in that section as only human error? I don't see it... Commented Jun 17, 2014 at 21:50
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    The "Association with Murphy" section does definitely suggest that the origin was a person doing the wrong thing every time as you say, but it is merely one of many theories as to the origin of the common phrase, and not a discussion of the term phrase (In my opinion). If you disagree, I'd be interesting in learning. Probably in chat though since I think we're no longer quite on topic. Commented Jun 17, 2014 at 21:53

In that situation, I use the phrase 'perfect storm'. As in:

I was unprepared and late for the meeting already, and then he told me it was moved up an hour. It was the perfect storm.

Of course, you cannot use it in a formal context, but otherwise it comes close to conveying the meaning you want.

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    Thanks Tushar, but a Perfect Storm is a confluence of events coming together to make a situation far worse. This isn't to say the situation is the exact opposite of optimal.
    – CLockeWork
    Commented Jun 19, 2014 at 8:29
  • I know it's not the ideal antonym. That's why I said "I'd use..." and "comes close".
    – Tushar Raj
    Commented Jun 19, 2014 at 10:24
  • I'm sorry, @Tushar. It's more that I don't see how a perfect storm relates at all :(
    – CLockeWork
    Commented Jun 19, 2014 at 15:43

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