(1):

(n.) Any sheathlike covering, organ, or part.

(2):

(n.) A case for the reception of a sword, hunting knife, or other long and slender instrument; a scabbard.

(3):

(n.) The base of a leaf when sheathing or investing a stem or branch, as in grasses.

(4):

(n.) One of the elytra of an insect.