Proof by intimidation (or argumentum verbosium) is a jocular phrase used mainly in mathematics to refer to a style of presenting a purported mathematical proof by giving an argument loaded with jargon and appeal to obscure results, so that the audience is simply obliged to accept it, lest they have to admit their ignorance and lack of understanding.
The phrase is also used when the author is an authority in his field presenting his proof to people who respect a priori his insistence that the proof is valid or when the author claims that his statement is true because it is trivial or because he simply says so. Usage of this phrase is for the most part in good humour, though it also appears in serious criticism.
"Proof by intimidation" is also cited by critics of junk science to describe cases in which scientific evidence is thrown aside in favour of a litany of tragic individual cases presented to the public by articulate advocates who pose as experts in their field.
Gian-Carlo Rota claimed in a memoir that the expression "proof by intimidation" was coined by Mark Kac to describe a technique used by William Feller in his lectures.