exhaust
n. uncountablen. the waste gas that comes out of an engine when it is running. It also refers to the pipe under a car that lets these gases out.
n. the waste gases expelled from an engine as a byproduct of internal combustion; by extension, the system of pipes through which these gases are released.
Black smoke came out of the car's exhaust.
The mechanic needs to replace the rusted exhaust pipe before the car can pass its safety inspection.
Environmental regulations have forced manufacturers to develop sophisticated filtration systems to reduce the volume of toxic particulates found in diesel exhaust.
From Latin exhaustus, past participle of exhaurīre (“to draw out, drink up, empty, exhaust”), from ex (“out”) + haurīre (“to draw (especially water), drain”).
Uncountable when referring to the gas itself; countable when referring to the mechanical system or pipe.