A weasel word, or anonymous authority, is an informal term for words and phrases aimed at creating an impression that something specific and meaningful has been said, when in fact only a vague or ambiguous claim has been communicated. Examples include the phrases "some people say", "it is thought", and "researchers believe". Using weasel words may allow one to later deny any specific meaning if the statement is challenged, because the statement was never specific in the first place. Weasel words can be a form of tergiversation and may be used in advertising, (popular) science, opinion pieces and political statements to mislead or disguise a biased view or unsubstantiated claim.

Weasel words can harshen or over-state a controversial statement. An example of this is using terms like "somewhat" or "in most respects", which make a sentence more ambiguous than it would be without them.