A duct for hot air which runs along the side of a building or room. Obsolete. rare.

A duct or pipe for the conveyance of heat by means of steam, hot water, or air.

a hot-air pipe laid along the floor of a conservatory.

Each of the pipes by which hot air is conveyed in a ‘stove’ or hothouse.

A hot-air channel in a green-house, etc.; a flue.

In early use = chimney, n.; subsequently a smoke-duct in a chimney. Hence extended to denote a channel of various kinds for conveying heat, etc., esp.…

a pipe carrying hot water, esp. in the heating system of a building.

A vertical pipe for carrying a fluid upwards; spec. (a) one carrying water or steam from one floor to another in a building; (b) one extending…

the pipe by which hot water leaves the boiler in a system of heating (see also quot. 1967 flow-blue n.).