(1):

(a.) Performed by, or dependent on, a muscle or the muscles.

(2):

(a.) Well furnished with muscles; having well-developed muscles; brawny; hence, strong; powerful; vigorous; as, a muscular body or arm.

(3):

(a.) Of or pertaining to a muscle, or to a system of muscles; consisting of, or constituting, a muscle or muscles; as, muscular fiber.