Source : Webster's Revised Unabridged Dictionary (1913)

Trimeter \Trim"e*ter\, a. [L. trimetrus, Gr. ?; ? (see {Tri-}) +
   {?} measure. See {Meter} measure.] (Pros.)
   Consisting of three poetical measures. -- n. A poetical
   division of verse, consisting of three measures. --Lowth.