/skawp/ , n.
any of several diving ducks of the genus Aythya, esp. A. marila (greater scaup) , of the Northern Hemisphere, having a bluish-gray bill. Also called scaup duck .
[ 1665-75; by ellipsis from scaup duck, prob. with Scots, N dial. scaup, scalp mussel bed (of uncert. orig.) ]