The definition of a frenum is a fold of skin or a mucous membrane that limits or controls the movement of an organ or body part.
The small piece of pink skin that attaches the tongue to the bottom of the mouth is an example of a frenum.
nounpl. fre·nums or fre·na
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 that connects the underside of the tongue to the floor of the mouth.
Origin of frenumLatin frēnum, bridle, from frendere, to grind; see ghrendh- in Indo-European roots.