whale·bone / ˈ(h)wālˌbōn/ • n. an elastic horny substance that grows in a series of thin parallel plates in the upper jaw of some whales and is used by them to strain plankton from the seawater. Also called baleen. ∎  strips of this substance, much used formerly as stays in corsets and dresses: [as adj.] a whalebone bodice. ∎  bone or ivory from a whale or walrus.

whalebone (baleen) Transverse horny plates hanging down from the upper jaw on each side of the mouth of the toothless whales (see Cetacea), forming a sieve. Water, containing plankton on which the whale feeds, enters the open mouth and is then expelled with the mouth slightly closed, so that food is retained on the baleen plates.