The Collaborative International Dictionary of English v.0.48:

Decrepitation \De*crep`i*ta"tion\, n. [Cf. F.
   d['e]cr['e]pitation.]
   The act of decrepitating; a crackling noise, such as salt
   makes when roasting.
   [1913 Webster]

WordNet (r) 3.0 (2006):

decrepitation
    n 1: the crackling or breaking up of certain crystals when they
         are heated