frenum

noun, plural fre·na [free-nuh] /ˈfri nə/. Anatomy, Zoology.

1. a fold of membrane that checks or restrains the motion of a part, as the fold on the underside of the tongue.

noun plural -na (-nə)

1. a variant spelling (esp US) of fraenum

n. pl. fre•nums

1. A membranous fold of skin or mucous membrane that supports or restricts the movement of a part or organ, such as the small band of tissue connecting the tongue to the floor of the mouth.
2. An anatomical structure resembling such a fold.