The Collaborative International Dictionary of English v.0.48:

napalm \napalm\ (n[=a]"p[aum]m), n.
   A highly incediary liquid consisting of gasoline jelled with
   aluminum soaps, used as a weapon of war in fire bombs and
   flame throwers.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

napalm
    n 1: gasoline jelled with aluminum soaps; highly incendiary
         liquid used in fire bombs and flamethrowers