The Collaborative International Dictionary of English v.0.48:

Piquant \Pi"quant\, a. [F., p. pr. of piquer to prick or sting.
   See Pike.]
   Stimulating to the taste; giving zest; tart; sharp; pungent;
   as, a piquant anecdote. "As piquant to the tongue as salt."
   --Addison. "Piquant railleries." --Gov. of Tongue.
   [1913 Webster]

WordNet (r) 3.0 (2006):

piquant
    adj 1: having an agreeably pungent taste [syn: piquant,
           savory, savoury, spicy, zesty]
    2: engagingly stimulating or provocative; "a piquant wit";
       "salty language" [syn: piquant, salty]
    3: attracting or delighting; "an engaging frankness"; "a piquant
       face with large appealing eyes" [syn: engaging, piquant]