The Collaborative International Dictionary of English v.0.48:

Fluency \Flu"en*cy\, n. [L. fluentia: cf. F. fluence. See
   Fluent.]
   The quality of being fluent; smoothness; readiness of
   utterance; volubility.
   [1913 Webster]

         The art of expressing with fluency and perspicuity.
                                                  --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fluency
    n 1: powerful and effective language; "his eloquence attracted a
         large congregation"; "fluency in spoken and written English
         is essential"; "his oily smoothness concealed his guilt
         from the police" [syn: eloquence, fluency,
         smoothness]
    2: skillfulness in speaking or writing [ant: disfluency]
    3: the quality of being facile in speech and writing [syn:
       fluency, volubility, articulateness]

Moby Thesaurus II by Grady Ward, 1.0:

180 Moby Thesaurus words for "fluency":
   Atticism, abundance, affluence, afflux, affluxion, amplitude,
   appropriateness, articulateness, big mouth, candor, chasteness,
   chastity, chylifaction, chylification, clarity, classicalism,
   classicism, clearness, cloud of words, comeliness, command,
   communicativeness, concourse, confluence, conflux, control,
   conversableness, copiousness, correctness, course, crosscurrent,
   current, defluxion, diffuseness, diffusion, diffusiveness, dignity,
   directness, discrimination, distinction, downflow, downpour, drift,
   driftage, ease, effortlessness, effusion, effusiveness, elegance,
   elegancy, eloquence, extravagance, exuberance, facility, fecundity,
   felicitousness, felicity, fertility, finish, fittingness, flow,
   flow of words, flowing, flowing periods, flowing tongue,
   fluent tongue, fluidity, fluidness, flux, flux de bouche,
   flux de paroles, flux of words, fluxility, fluxion, formlessness,
   frankness, garrulity, garrulousness, gassiness, gift of gab,
   glibness, good taste, grace, gracefulness, gracility,
   gregariousness, gush, gushiness, gushing, inflow, juiciness,
   lactation, lactescence, limpidity, liquefaction, liquidness,
   logorrhea, long-windedness, loose tongue, loquaciousness,
   loquacity, lucidity, macrology, milkiness, mill run, millrace,
   moisture, naturalness, neatness, onrush, onward course, openness,
   outflow, outpour, overflow, palilogy, pellucidity, perspicuity,
   plainness, pleonasm, poetry, polish, prodigality, productivity,
   profuseness, profusion, prolificacy, prolificity, prolixity,
   propriety, purity, race, rampancy, rankness, redundancy,
   refinement, reiteration, reiterativeness, repetition for effect,
   repetitiveness, restraint, rheuminess, run, rush, sappiness,
   seemliness, serosity, set, simplicity, slickness, slush,
   smoothness, sociability, spate, spate of words,
   straightforwardness, stream, succulence, superabundance,
   superfluity, superflux, suppuration, surge, talkativeness, taste,
   tastefulness, tautology, teemingness, terseness, tide, tirade,
   trend, unaffectedness, undercurrent, undertow, verbosity,
   volubility, water flow, wateriness, windiness