Definitions for "firebrick"
a brick made of fire clay, used for lining e.g. furnaces and chimneys.
A refractory brick which meets the requirements of Standard No. 37-1. UBC.
A brick capable of withstanding high temperatures without deforming. 'Insulating firebricks' have the additional advantage of acting as good insulators due to the large pockets of air in the matrix of the brick. There are many different kinds of firebricks available, some very expensive. Types are categorized for their heat duty and the types of materials and atmospheres they must come into contact with.