1 Anatomy a small fold or ridge of tissue which supports or checks the motion of the part to which it is attached, in particular a fold of skin beneath the tongue, or between the lip and the gum.
2 Entomology (in some moths and butterflies) a bristle or row of bristles on the edge of the hindwing which keeps it in contact with the forewing.
Origin:
early 18th century: modern Latin, diminutive of Latin frenum 'bridle'
frenulum in other Oxford dictionaries
Definition of frenulum in the US English dictionary
