Any form of expression in which language is manipulated for rhetorical effect. Around ad 95, Quintilian defined the figure of speech as ‘a departure from the simple and straightforward method of expression.’ He listed four types of rhetorical deviation (mutatio): adjectio or addition, detractio or omission (see deletion), transmutatio or rearrangement (see transposition), and immutatio or substitution. In classical rhetoric, figures of speech were traditionally divided into schemes and tropes. Schemes are patterns of expression. They include: alliteration, anaphora, antithesis, asyndeton (see deletion), and climax. Tropes radically transform the meaning of words. These include: allegory, conceit, hyperbole, irony, metaphor, metonymy, onomatopoeia, oxymoron, paradox, personification, pun, rhetorical question, simile, and synecdoche. However, nowadays in many contexts the term trope is synonymous with figure of speech.
http://www.aber.ac.uk/media/Documents/S4B/sem07.html Rhetorical tropes