The Collaborative International Dictionary of English v.0.48:

Locution \Lo*cu"tion\ (l[-o]*k[=u]"sh[u^]n), n. [L. locutio, fr.
   loqui to speak: cf. F. locution. ]
   Speech or discourse; a phrase; a form or mode of expression.
   " Stumbling locutions." --G. Eliot.
   [1913 Webster]

         I hate these figures in locution,
         These about phrases forced by ceremony.  --Marston.
   [1913 Webster]

WordNet (r) 3.0 (2006):

locution
    n 1: a word or phrase that particular people use in particular
         situations; "pardon the expression" [syn: saying,
         expression, locution]

Moby Thesaurus II by Grady Ward, 1.0:

81 Moby Thesaurus words for "locution":
   adjectival phrase, antonym, articulation, choice of words, clause,
   composition, construction, dialect, diction, expression,
   formulation, free form, grammar, headed group, homograph, homonym,
   homophone, idiom, idiotism, language, langue, lexeme, lingo,
   lingua, linguistic act, linguistic form, logos, manner of speaking,
   metonym, minimum free form, monosyllable, noun phrase, paragraph,
   parlance, parol, parole, peculiar expression, period,
   personal usage, phonation, phrasal idiom, phrase, phraseology,
   phrasing, polysyllable, rhetoric, sentence, sequence of phonemes,
   set phrase, speaking, speech, speech act, standard phrase, string,
   syllable, synonym, syntactic structure, talk, term,
   the spoken word, tongue, turn of expression, turn of phrase, usage,
   use of words, usus loquendi, utterance, utterance string,
   verb complex, verb phrase, verbalism, verbiage, verbum, vocable,
   voice, way of speaking, word, word of mouth, word-group, wordage,
   wording