The Collaborative International Dictionary of English v.0.48:

Eloquent \El"o*quent\, a. [F. ['e]loquent, L. eloquens, -entis,
   p. pr. of eloqui to speak out, declaim; e + loqui to speak.
   See Loquacious.]
   1. Having the power of expressing strong emotions or forcible
      arguments in an elevated, impassioned, and effective
      manner; as, an eloquent orator or preacher.
      [1913 Webster]

            O Death, all-eloquent! You only prove
            What dust we dote on when 't is man we love. --Pope.
      [1913 Webster]

   2. Adapted to express strong emotion or to state facts
      arguments with fluency and power; as, an eloquent address
      or statement; an eloquent appeal to a jury.
      [1913 Webster]

WordNet (r) 3.0 (2006):

eloquent
    adj 1: expressing yourself readily, clearly, effectively; "able
           to dazzle with his facile tongue"; "silver speech" [syn:
           eloquent, facile, fluent, silver, silver-
           tongued, smooth-spoken]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "eloquent":
   Ciceronian, Demosthenian, Demosthenic, Tullian, affecting, ardent,
   articulate, cogent, convincing, declamatory, effective,
   elocutionary, expressive, facile, facund, felicitous, fervent,
   fervid, fluent, forceful, forensic, free-speaking, free-spoken,
   glib, graphic, high, impassioned, impressive, incisive, indicative,
   lofty, loud-speaking, loud-spoken, meaningful, oratorical,
   outspoken, passionate, persuasive, plain-speaking, plain-spoken,
   poignant, potent, powerful, pregnant, revealing, rhetorical, rich,
   sententious, significant, silver, silver-tongued, slick, smooth,
   smooth-spoken, smooth-tongued, soft-speaking, soft-spoken,
   speaking, spellbinding, striking, suggestive, talkative, talking,
   telling, touching, trenchant, true-speaking, vivid, vocal, voluble,
   well-spoken