Handwaving is a pejorative label applied to the action of displaying the appearance of doing something, when actually doing little, or nothing. It is often used in working situations where results are expected, but no work is actually accomplished. Handwaving can be an idiomatic term, and it can also be a literal descriptive term for the use of excessive body language gestures that may be perceived as lacking productivity in communication or other effort. If the opponent in a debate uses the term, it is meant as a shorthand way to accuse the proponent of having committed an informal fallacy. In this sense, it is also as if a participant is waving their hands as to discourage an insect that is flying around their head, so are they waving away questions. The superlative expressions for the term, such as ‘vigorous handwaving’ or ‘furious handwaving,’ are used to imply that the handwaver lacks confidence in the information being conveyed, and cannot actually convey the essence or core of his argument.
Handwaving arguments often include order-of-magnitude estimates and dimensional analysis. Competent well-intentioned researchers and professors rely on handwaving when, given a limited time, a large result must be shown and minor technical details cannot be given much attention. ‘Back-of-the-envelope’ calculations are approximate ways to get an answer by over-simplification and are compatible with handwaving. By extension, handwaving is used in speculative fiction criticism to refer to a plot device (e.g., a scientific discovery, a political development, or rules governing the behavior of a fictional creature) that is left unexplained or sloppily explained because it is convenient to the story, with the implication that the writer is aware of the logical weakness but hopes the reader will not notice or will suspend disbelief. The fictional material ‘handwavium’ is sometimes referred to in situations where the solution requires access to a substance that is physically impossible to create as it defies physics but is convenient to solving a problem in the story.
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