Hypertext Webster Gateway: "crissum"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Crissum \Cris"sum\ (kr?s"s?m),, n.; pl. {Crissa} (-s?). [NL.;
cf. L. crisso to move the haunches.] (Zo["o]l.)
That part of a bird, or the feathers, surrounding the cloacal
opening; the under tail coverts.
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