Dictionary.com
definitions

air brick

noun
  1. a ceramic or metal unit the size of a brick, open at the sides for admitting air to a building interior.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for airbrick

airbrick

noun
  1. mainly British a brick with holes in it, put into the wall of a building for ventilation
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012