What is the term for the mistaken substitution of a word for a similar-sounding word?

The term that describes the mistaken substitution of a word for a similar-sounding word is malapropism. This phenomenon occurs when a speaker uses a word that sounds similar to the intended word but has a completely different meaning, often resulting in a humorous or nonsensical effect. Malapropisms highlight the humorous aspects of language and can provide insight into the speaker's knowledge and understanding of words.

For instance, if someone says, "He's the pineapple of politeness," when they meant "pinnacle," this is a classic example of a malapropism. The phonetic confusion creates an amusing twist, showcasing the speaker's error while also illustrating the richness of language.

In contrast, the other terms do not fit this specific definition. Solecism refers to grammatical mistakes or nonstandard language use that may confuse meaning rather than simply swap similar-sounding words. Paronomasia, on the other hand, concerns puns and wordplay but is not strictly about mistaken substitution. Lastly, an oxymoron combines contradictory terms for effect, such as 'deafening silence,' rather than focusing on the error in word choice.