marine crustaceans with feathery food-catching appendages; free-swimming as larvae; as adults form a hard shell and live attached to submerged surfaces
a rigid circular band of metal or wood or other material used for holding or fastening or hanging or pulling; "there was still a rusty iron hoop for tying a horse"
conducive to good health of body or mind; "a healthful climate"; "a healthful environment"; "healthful nutrition"; "healthful sleep"; "Dickens's relatively healthful exuberance"