The Collaborative International Dictionary of English v.0.48:

Trigeminal \Tri*gem"i*nal\, a. [See Trigeminous.] (Anat.)
   Of, pertaining to, or designating, the fifth pair of cranial
   nerves, which divide on each side of the head into three main
   branches distributed to the orbits, jaws, and parts of the
   mouth; trifacial.
   [1913 Webster]

WordNet (r) 3.0 (2006):

trigeminal
    n 1: the main sensory nerve of the face and motor nerve for the
         muscles of mastication [syn: trigeminal, trigeminal
         nerve, trigeminus, nervus trigeminus, fifth cranial
         nerve]