Tetrabasic \Tet`ra*bas"ic\, a. [Tetra- + basic.]

(Chem.) Capable of neutralizing four molecules of a monacid base; having four hydrogen atoms capable of replacement by bases; quadribasic; -- said of certain acids; thus, normal silicic acid, Si(OH)4, is a tetrabasic acid.

Source: Webster's Revised Unabridged Dictionary (1913)