The Collaborative International Dictionary of English v.0.48:
Neurilemma \Neu`ri*lem"ma\, n. [NL., from Gr. ney^ron nerve + ? peel, skin.] (Anat.) (a) The delicate outer sheath of a nerve fiber; the primitive sheath. (b) The perineurium. [1913 Webster]WordNet (r) 3.0 (2006):
neurilemma n 1: thin membranous sheath around a nerve fiber [syn: neurolemma, neurilemma]