pterygoid muscle

: either of two muscles extending from the sphenoid bone to the lower jaw:

a : a muscle that arises from the greater wing of the sphenoid bone and from the outer surface of the lateral pterygoid plate, is inserted into the condyle of the mandible and the articular disk of the temporomandibular joint, and acts as an antagonist of the masseter, temporalis, and medial pterygoid muscles

— called also external pterygoid muscle, lateral pterygoid muscle

b : a muscle that arises from the inner surface of the lateral pterygoid plate and from the palatine and maxillary bones, is inserted into the ramus and the gonial angle, cooperates with the masseter and temporalis in elevating the lower jaw, and controls certain lateral and rotary movements of the jaw

— called also internal pterygoid muscle, medial pterygoid muscle