The Collaborative International Dictionary of English v.0.48:

Simile \Sim"i*le\, n.; pl. Similes. [L., from similis. See
   Similar.] (Rhet.)
   A word or phrase by which anything is likened, in one or more
   of its aspects, to something else; a similitude; a poetical
   or imaginative comparison.
   [1913 Webster]

         A good swift simile, but something currish. --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

simile
    n 1: a figure of speech that expresses a resemblance between
         things of different kinds (usually formed with `like' or
         `as')

Moby Thesaurus II by Grady Ward, 1.0:

105 Moby Thesaurus words for "simile":
   accordance, affinity, agreement, alikeness, allegory, alliance,
   alliteration, allusion, anacoluthon, anadiplosis, analogy,
   anaphora, anastrophe, antiphrasis, antithesis, antonomasia, aping,
   apophasis, aporia, aposiopesis, apostrophe, approach,
   approximation, assimilation, balancing, catachresis, chiasmus,
   circumlocution, climax, closeness, community, comparability,
   comparative anatomy, comparative degree, comparative grammar,
   comparative judgment, comparative linguistics,
   comparative literature, comparative method, compare, comparing,
   comparison, conformity, confrontation, confrontment, contrast,
   contrastiveness, conversion, copying, correlation, correspondence,
   distinction, distinctiveness, ecphonesis, emphasis, exclamation,
   gemination, hypallage, hyperbaton, hyperbole, identity, imitation,
   inversion, irony, likeness, likening, litotes, malapropism,
   matching, meiosis, metaphor, metonymy, mimicking, nearness,
   onomatopoeia, opposing, opposition, oxymoron, parallelism,
   paregmenon, parenthesis, parity, periphrasis, personification,
   pleonasm, preterition, prolepsis, proportion, regression, relation,
   repetition, resemblance, sameness, sarcasm, semblance, similarity,
   similitude, simulation, spoonerism, syllepsis, symploce,
   synecdoche, trope of comparison, weighing, zeugma