Plates or blades of whalebone, from two to twelve feet long, and sometimes a foot wide, which in certain whales (Balaenoidea) are attached side by side along the upper jaw, and form a fringelike sieve by which the food is retained in the mouth. (biology-online.org)
2. A filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale’s mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food source for the whale. (wikipedia.org)
3. A horny keratinous substance found in two rows of transverse plates which hang down from the upper jaws of baleen whales. (merriam-webster.com)
Word origin: From Old French baleine (“whale, whalebone”), from Latin balaena (“whale”), from Ancient Greek φάλαινα (“whale”).