Source : Webster's Revised Unabridged Dictionary (1913)

Tetratomic \Tet`ra*tom"ic\, a. [Tetra- + atomic.] (Chem.)
   (a) Consisting of four atoms; having four atoms in the
       molecule, as phosphorus and arsenic.
   (b) Having a valence of four; quadrivalent; tetravalent;
       sometimes, in a specific sense, having four hydroxyl
       groups, whether acid or basic.