Source : Webster's Revised Unabridged Dictionary (1913)

Cachalot \Cach"a*lot\, n. [F. cachalot.] (Zo["o]l.)
   The sperm whale ({Physeter macrocephalus}). It has in the top
   of its head a large cavity, containing an oily fluid, which,
   after death, concretes into a whitish crystalline substance
   called spermaceti. See {Sperm whale}.

Source : WordNet®

cachalot
     n : large whale with a large cavity in the head containing
         spermaceti and oil; also a source of ambergris [syn: {sperm
         whale}, {black whale}, {Physeter catodon}]