(Science: zoology) A very large toothed whale (physeter macrocephalus), having a head of enormous size. The upper jaw is destitute of teeth. In the upper part of the head, above the skull, there is a large cavity, or case, filled with oil and spermaceti. This whale sometimes grows to the length of more than eighty feet. It is found in the warmer parts of all the oceans. Called also cachalot, and spermaceti whale. Pygmy sperm whale, a toothed cetacean (Hyperoodon bidens), found on both sides of the atlantic and valued for its oil. The adult becomes about twenty-five feet long, and its head is very large and thick. Called also bottle-nosed whale.