Which expression does not mean what the individual words suggest, such as "take the bull by the horns"?

The expression that does not mean what the individual words suggest is an idiom. Idioms are phrases or expressions that convey a meaning that is different from the literal interpretation of the words used. For example, "take the bull by the horns" means to confront a difficult situation directly, which does not align with the literal meaning of the individual words, making this phrase an idiom.

In contrast, proverbs, metaphors, and similes often either reflect a more straightforward relationship between the words or maintain a degree of metaphorical meaning that can still be inferred from the individual terms. Proverbs generally convey a universal truth or moral lesson, metaphors draw direct comparisons without using "like" or "as," and similes do use "like" or "as" to compare two distinct things. However, their meanings often relate more clearly to their components compared to idioms, which can confound the reader by presenting a non-literal interpretation.