Caliducts were a kind of pipes, or canals, placed along the walls of houses and apartments, used by the ancients for the conveyance of heat to several remote parts of the house, from one common furnace. ...
• (n.) A pipe or duct used to convey hot air or steam.
Cal'i·duct noun [ See Caloriduct .] A pipe or duct used to convey hot air or steam. « Subterranean caliducts have been introduced. Evelyn. » 
caliduct, caleduct A duct or pipe for the conveyance of heat by means of steam, hot water, or air; used by the ancient Romans for the conveyance of heat to several remote parts of their houses, from one common furnace.