The Collaborative International Dictionary of English v.0.48:

Gusto \Gus"to\, n. [It. or Sp., fr. L. gustus; akin to E.
   choose. Cf. 2d Gust, Go[^u]t.]
   Nice or keen appreciation or enjoyment; relish; taste; fancy;
   as, he ate it with gusto. --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

gusto
    n 1: vigorous and enthusiastic enjoyment [syn: gusto,
         relish, zest, zestfulness]

Moby Thesaurus II by Grady Ward, 1.0:

137 Moby Thesaurus words for "gusto":
   activity, affection, alacrity, amusement, animal pleasure,
   animal spirits, animation, anxiety, anxiousness, appetite,
   appreciation, ardency, ardor, avidity, avidness, bodily pleasure,
   breathless impatience, brio, briskness, capersomeness,
   carnal delight, cheerful readiness, coltishness, comfort, content,
   contentment, coziness, creature comforts, crush, delectation,
   delight, eagerness, ease, ecstasy, elan, endpleasure, enjoyment,
   entertainment, enthusiasm, esprit, euphoria, excitement,
   exuberance, fervency, fervidness, fervor, fire, fondness,
   forepleasure, forwardness, friskiness, frolicsomeness, fruition,
   fun, furor, fury, gaiety, gamesomeness, gayness, glow,
   gratification, great satisfaction, gust, heart, heartiness,
   hearty enjoyment, heat, impassionedness, impatience, impetuosity,
   impetus, infatuation, intellectual pleasure, joie de vivre,
   keen desire, keen pleasure, keenness, kicks, life, likes, liking,
   liveliness, love, lustiness, luxury, mettle, palate, passion,
   passionateness, perkiness, pertness, physical pleasure,
   piss and vinegar, playfulness, pleasure, promptness, quickness,
   quiet pleasure, readiness, relish, robustness, rollicksomeness,
   rompishness, satisfaction, savor, self-gratification,
   self-indulgence, sensual pleasure, sensuous pleasure,
   sexual pleasure, skittishness, soul, spirit, spiritedness, spirits,
   sportiveness, sprightliness, sweetness of life, taste, titillation,
   upclimb, vehemence, verve, vigor, vim, vitality, vivacity,
   voluptuousness, warmth, warmth of feeling, weakness, well-being,
   zeal, zealousness, zest, zestfulness, zip