trigeminus n the main sensory nerve of the face and motor nerve for the muscles of mastication Usage(s) Diseased teeth, sinuses, nose or throat may affect the trigeminus, arouse a prolonged fit of sneezing. His hosts say that the Soviet leader was suffering from a recurring affliction of the trigeminus, the nerve controlling the lower jaw. Synonym(s) trigeminal trigeminal nerve nervus trigeminus fifth cranial nerve