The Collaborative International Dictionary of English v.0.48:

fibreboard \fibreboard\ n.
   Same as fiberboard. [mostly British usage]
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

fibreboard
    n 1: wallboard composed of wood chips or shavings bonded
         together with resin and compressed into rigid sheets [syn:
         fiberboard, fibreboard, particle board]