(1):

(n.) A hollow cut in anything; a nick; an indentation.

(2):

(n.) A narrow passage between two elevation; a deep, close pass; a defile; as, the notch of a mountain.

(3):

(v. t.) To cut or make notches in; to indent; also, to score by notches; as, to notch a stick.

(4):

(v. t.) To fit the notch of (an arrow) to the string.