Tri`a*tom"ic (?), a. [Pref. tri- + atomic.] Chem. (a)
Having three atoms; -- said of certain elements or radicals.
(b)
Having a valence of three; trivalent; sometimes, in a specific sense, having three hydroxyl groups, whether acid or basic; thus, glycerin, glyceric acid, and tartronic acid are each triatomic.
© Webster 1913.