The Collaborative International Dictionary of English v.0.48:

Crackling \Crac"kling\ (kr?k"kl?ng), n.
   1. The making of small, sharp cracks or reports, frequently
      repeated.
      [1913 Webster]

            As the crackling of thorns under a pot, so is the
            laughter of the fool.                 --Eccl. vii.
                                                  6.
      [1913 Webster]

   2. The well-browned, crisp rind of roasted pork.
      [1913 Webster]

            For the first time in his life he tested crackling.
                                                  --Lamb.
      [1913 Webster]

   3. pl. Food for dogs, made from the refuse of tallow melting.
      [1913 Webster] Crack-loo

WordNet (r) 3.0 (2006):

crackling
    n 1: the residue that remains after animal fat has been rendered
         [syn: greaves, crackling]
    2: the sharp sound of snapping noises [syn: crackle,
       crackling, crepitation]