A malapropism is when someone accidentally uses the wrong word because it sounds similar to the word they meant to say, often creating a funny or confusing result. The mix-up usually happens with words that sound alike but have completely different meanings.

For example, if someone says “Texas has a very human climate” when they mean humid, that's a malapropism. Or if a student announces they're studying “Pygmy Indians” instead of Pygmalion in English class. The humor comes from the fact that the wrong word is close enough in sound that you can tell what the speaker meant, but different enough in meaning to create an absurd image. When you picture a human climate instead of a humid one, it sounds ridiculous because climates aren't human.

The word comes from a character named Mrs. Malaprop in an old play who constantly made these mistakes. She would say things like “she's as headstrong as an allegory on the banks of the Nile” when she meant alligator.

Malapropisms are different from simple mispronunciations. They're specifically about substituting one real word for another real word that sounds similar but means something entirely different, creating an unintentionally comic effect.