'Carboxyl' definitions:

Definition of 'carboxyl'

(from WordNet)
adjective
Relating to or containing the carboxyl group or carboxyl radical [syn: carboxyl, carboxylic]
noun
The univalent radical -COOH; present in and characteristic of organic acids [syn: carboxyl, carboxyl group]

Definition of 'Carboxyl'

From: GCIDE
  • Carboxyl \Car*box"yl\ (k[aum]r*b[o^]ks"[i^]l), n. [Carbon + oxygen + -yl.] (Chem.) The complex radical, CO.OH, regarded as the essential and characteristic constituent which all oxygen acids of carbon (as formic, acetic, benzoic acids, etc.) have in common; -- called also oxatyl. [1913 Webster]