I've been hearing term "hand-waving" thrown around a lot, especially when my peers describe their CS(computer science) classes. Does anyone know what that term means in this context?

(also a little background on where the term came from would help too!)

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    "Waive" means relinquish or forego, so the "hand-waiving" in your title means, to do without hands. Oct 12, 2011 at 1:53

2 Answers 2


Wiktionary says it better than I can, describing "hand waving" in this context as:

Discussion or argumentation involving approximation, vagueness, educated guessing, or the attempt to explain or excuse vagaries.

The phrase is purely idiomatic. Picture the hand gestures of someone speaking on a topic that perhaps is vague or confusing, or of which the speaker is unfamiliar or poorly prepared. Certainly brings back memories of my computer science classes!

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    Hand waving is what happens in a lecture after a professor writes a theorem on a blackboard and tries to "demonstrate its validity" via gestures over diagrams and equations, often accompanied with the statement "It can be easily shown that..."
    – Firstrock
    Oct 12, 2011 at 2:33

The Jargon File has a good definition of 'handwave':

handwave: /hand wayv/
[poss. from gestures characteristic of stage magicians]

  1. v. To gloss over a complex point; to distract a listener; to support a (possibly actually valid) point with blatantly faulty logic.

  2. n. The act of handwaving. “Boy, what a handwave!”

If someone starts a sentence with “Clearly...” or “Obviously...” or “It is self-evident that...”, it is a good bet he is about to handwave (alternatively, use of these constructions in a sarcastic tone before a paraphrase of someone else's argument suggests that it is a handwave). The theory behind this term is that if you wave your hands at the right moment, the listener may be sufficiently distracted to not notice that what you have said is bogus. Failing that, if a listener does object, you might try to dismiss the objection with a wave of your hand.

The use of this word is often accompanied by gestures: both hands up, palms forward, swinging the hands in a vertical plane pivoting at the elbows and/or shoulders (depending on the magnitude of the handwave); alternatively, holding the forearms in one position while rotating the hands at the wrist to make them flutter. In context, the gestures alone can suffice as a remark; if a speaker makes an outrageously unsupported assumption, you might simply wave your hands in this way, as an accusation, far more eloquent than words could express, that his logic is faulty.

Jargon File: Handwave

Not to be confused with 'waving a dead chicken'.

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