noun.
The univalent group, −COOH, the functional group characteristic of all organic acids.
The Century Dictionary and Cyclopedia
noun.
A hypothetical organic radical having the formula COOH.
the GNU version of the Collaborative International Dictionary of English
noun.
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.