Crissum

noun

1. The feathers or area under the tail of a bird surrounding the cloacal opening.
2. In ornithology, the region between the anus and the tail of a bird; especially, the feathers of this region, the vent-feathers or under tail-coverts, collectively. See cut under bird.
3. That part of a bird, or the feathers, surrounding the cloacal opening; the under tail coverts.
4. The area of feathers on a bird that surround its cloaca.