[L. sperma, seed; and cetus, a whale.] A kind of fat from the head of the sperm whale used in making candles, ointments, and cosmetics. It is a semi-fluid substance which, on being taken from the animal, hardens as it cools. The large head is partly occupied by a cavity containing spermaceti, and other cavities throughout the body are also filled with it. It consists of salts of palmitic acid and ethal and hydrocarbon bases.