'firebrick' definitions:

Definition of 'firebrick'

From: WordNet
noun
Brick made of fire clay; used for lining e.g. furnaces and chimneys

Definition of 'firebrick'

From: GCIDE
  • firebrick \firebrick\ n. a brick made of fire clay, used for lining e.g. furnaces and chimneys. [WordNet 1.5]