frenulum

noun, plural fren·u·la [fren-yuh-luh] /ˈfrɛn yə lə/.

1. Anatomy, Zoology. a small frenum.
2. Entomology. a strong spine or group of bristles on the hind wing of many butterflies and moths, projecting beneath the forewing and serving to hold the two wings together in flight.

noun plural -la (-lə)

1. a strong bristle or group of bristles on the hind wing of some moths and other insects, by which the forewing and hind wing are united during flight
2. a small fraenum

n. pl. fren•u•la (-lə)

1. A small frenum or band of fibrous material.