Noun, pl. fraenulums, frenulums
1. A small fold of tissue that secures or restricts the motion of a mobile organ in the body. (wikipedia.org)
2. A small fold or ridge of tissue that 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. (Google Dictionary)
3. (In some moths and butterflies) A bristle or row of bristles on the edge of the hind wing that keeps it in contact with the forewing. (Google Dictionary)
Syn: Frenum, pl. frena
Word origin: Latin frēnulum, “little bridle”, the diminutive of frēnum.