Tribasic \Tri*ba"sic\, a. [Pref. tri- + basic.]

(Chem.) Capable of neutralizing three molecules of a monacid base, or their equivalent; having three hydrogen atoms capable of replacement by basic elements on radicals; -- said of certain acids; thus, citric acid is a tribasic acid.

Source: Webster's Revised Unabridged Dictionary (1913)