ˈkrisəm noun
( plural cris·sa -sə)
Etymology: New Latin, from Latin crissare, crisare to wiggle the backside while having sexual intercourse (said of a woman); akin to Old English hrith fever, scrīthan to go, move around, Old High German hritto fever, scrītan to go, step, Old Norse hrīth storm, attack, skrītha to creep, glide, Welsh cryd fever, ysgryd shiver, Lithuanian skrytis felly of a wheel, and probably to Latin curvus curved — more at crown
: the part of a bird surrounding the cloacal opening ; also : the feathers covering that region : the under tail coverts