The Collaborative International Dictionary of English v.0.48:

Spermaceti \Sper`ma*ce"ti\, n. [L. sperma sperm + cetus,gen.
   ceti, any large sea animal, a whale, Gr. ???. See Sperm,
   Cetaceous.]
   A white waxy substance obtained from cavities in the head of
   the sperm whale, and used making candles, oilments,
   cosmetics, etc. It consists essentially of ethereal salts of
   palmitic acid with ethal and other hydrocarbon bases. The
   substance of spermaceti after the removal of certain
   impurities is sometimes called cetin.
   [1913 Webster]

   Spermaceti whale (Zool.), the sperm whale.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

cachalot \cach"a*lot\, n. [F. cachalot.] (Zool.)
   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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spermaceti
    n 1: a white waxy substance from oil of the sperm whale