bracken or brake, common name for a tall fern (Pteridium aquilinum) with large triangular fronds, widespread throughout the world, often as a weed. It is considered poisonous to livestock when eaten in quantity, but the rootstocks and the young shoots, cooked, are used for food. Bracken is also a source of tannin and is used for thatching and as bedding for livestock. A beverage is made from the roots. The names bracken and brake are sometimes also applied to other large, coarse ferns and, as general terms, to a thicket of such plants. Bracken is classified in the division Polypodiophyta, class Polypodiopsida, order Filicales, family Polypodiaceae.