The Collaborative International Dictionary of English v.0.48:

carboxylic \car`box*yl"ic\ (k[aum]r`b[o^]ks*[i^]l"[i^]k), adj.
   (Chem.)
   of or pertaining to the carboxyl group; having a carboxyl
   group (written -COOH, -CO2H or -CO.OH); as, carboxylic
   acids are weakly acidic.

   Syn: carboxyl.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

carboxylic
    adj 1: relating to or containing the carboxyl group or carboxyl
           radical [syn: carboxyl, carboxylic]