Definition of "firebrick"

firebrick

noun
plural firebricks
1. a brick capable of withstanding high temperatures without deforming.
  Quotations
  Eastleigh Locomotive Works: Layout and functions of shops [...] Brick Shop: Manufacture of firebricks.
  1961 March, C. P. Boocock, “The organisation of Eastleigh Locomotive Works”, in Trains Illustrated, page 162
2. (computer science) The X11 color name of RGB hexadecimal value #B22222.