tri·basic \(ˈ)trī+\adjective Etymology:tri- + basic 1.: having three hydrogen atoms capable of replacement by basic atoms or radicals — used of acids (as phosphoric acid) 2.: containing three atoms of a univalent metal or their equivalent < tribasic sodium phosphate Na3PO4 > 3.: having three basic hydroxyl groups : able to react with three molecules of a monobasic acid — used of bases and basic salts • tri·basicity\|trī+\noun