duckweed

n [U] plant that forms on the surface of ponds, etc 浮萍（生在池塘等表面的植物）.

DSO, DT, dual, dual carriageway, dual-control, dual-purpose, duality, dub, dubbin, dubiety, dubious, ducal, duchess, duchy, duck, duck-boards, duck-yard, ducking, duckling, ducks and drakes, duct, ductile, ductility, ductless gland, dud, dude, dudgeon, duds, due, due to, duel, duellist, duenna, duet, duff, duffer, duffle (also duffel), duffle bag, duffle-coat, dug,