figure of speech

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An expression that uses language in a nonliteral way, such as a metaphor or synecdoche, or in a structured or unusual way, such as anaphora or chiasmus, or that employs sounds, such as alliteration or assonance, to achieve a rhetorical effect.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun idiomatic A word or phrase that departs from straightforward, literal language.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun language used in a figurative or nonliteral sense