'Hypoptilums' definitions:
Definition of 'Hypoptilums'
From: GCIDE
- Hypoptilum \Hy*pop"ti*lum\, n.; pl. L. Hypoptila, E. Hypoptilums. [NL., fr. Gr. "ypo` beneath + ? down.] (Zool.) An accessory plume arising from the posterior side of the stem of the contour feathers of many birds; -- called also aftershaft. See Illust. of Feather. [1913 Webster]