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Meaning of frenulum

fren•u•lum

Pronunciation: (fren'yu-lum), [key]
— pl. -la
  1. a small frenum.
  2. 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.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.