A slight smell or a gust of air, or to miss completely (like swinging at a baseball and not hitting it).
Origin uncertain, but possibly imitative in nature—the word itself sounds like air moving. First recorded in the 1600s with the sense of 'a breath of air,' and by the 1900s it was being used in baseball to mean a missed swing.
In baseball, a 'whiff' is when a batter swings and completely misses—and the word perfectly mimics that sound of air whooshing past the bat. Players actually adopted this onomatopoeia because the word itself sounds like what happens!
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