Source : Webster's Revised Unabridged Dictionary (1913)

Trigeminous \Tri*gem"i*nous\, a. [L. trigeminus born three
   together; tri- (see {Tri-}) + geminus twin. Cf.
   {Tergeminous}.]
   Born three together; being one of three born at the same
   birth; also, threefold. --E. Phillip?.