The Collaborative International Dictionary of English v.0.48:

fire-resistant \fire-resistant\ fire-resisting \fire-resisting\
fire-resistive \fire-resistive\adj.
   Not able to burn or able to burn only with difficulty.
   [Narrower terms: noncombustible (vs. combustible),
   incombustible]

   Syn: fireproof.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

fire-resisting
    adj 1: difficult to burn [syn: fire-retardant, fire-
           resistant, fire-resisting, fire-resistive]