Is it ok to use the word "killer" (as an adjective) in a semi-formal or even formal text like an ebook? For example, "this is the killer part," which essentially means that it is the most significant part.

If it isn't ok, can it be used within double-quotes to signify the usage of an informal term?

Thank you!

  • 3
    Only if it's intended to be read by programmers or gamers. I wouldn't use it in a semiformal briefing text for insurance executives or military officers, for instance. Commented Sep 4, 2013 at 15:01
  • :) How about an eBook that is slightly formal in tone owing to the nature of the topic being discussed?
    – Najeeb
    Commented Sep 4, 2013 at 15:05
  • 1
    There are so many versions of eBooks and readers and what "formal" means that it's impossible to answer in the abstract. All I can say is if you and your intended audience talk that way about that subject in what you consider a "formal" situation, go ahead and write that way, too. It's almost always better to say what you mean in the most clear and direct way. And then write down exactly what you said. Commented Sep 4, 2013 at 15:09
  • This question appears to be off-topic because it is about Writing advice.
    – TrevorD
    Commented Sep 4, 2013 at 15:43
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    Depends entirely on the context. “This is a killer book!” is perhaps not well-suited for formal contexts, but “This is a killer whale” is perfectly neutral and fine. Commented Sep 4, 2013 at 15:51

3 Answers 3


We're not supposed to give writing advice on EL&U, but . . ..

I have no problem with the use of killer. As with most decisions of this nature, a great deal depends on your audience, the content and theme of the ebook, and what you are trying to accomplish--in other words, your purpose in writing.

If your audience is young, and you want to show some currency in your language and prove you're "with it," then sure, why not. If the tenor/tone of your writing is informal, a bit playful, and, again, aimed at an audience which is familiar with and uses the expression, why not.

Audience considerations are key, in my opinion.


When I was younger I would have easily said, "That is a killer board." I think it was more skate/surf slang adopted and accepted by all younger people. Killer's meaning could vary but I would say that it means cool/awesome and cutting edge or really different.


It all depends on your audience, both intended and incidental, whether they'll understand "killer" as slang to mean "great, fantastic, the ultimate", or that they'll be totally confused or even offended. The phrase killer app is widely understood these days, but I would be concerned that killer used otherwise as an adjective could be misunderstood.

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