‘尾气’ literally means ‘tail gas’—‘尾’ (wěi) means ‘tail’ or ‘rear end’, and ‘气’ (qì) means ‘gas’ or ‘air’. Together, they refer to the gases emitted from the exhaust pipe (the ‘tail’) of vehicles such as cars, trucks, and motorcycles. This term is used almost exclusively in environmental, public health, and transportation contexts to describe harmful emissions like carbon monoxide, nitrogen oxides, and particulate matter.

In everyday Chinese, ‘尾气’ appears in discussions about air pollution, vehicle emissions standards, green energy policies, and urban smog. It’s a technical yet common word—frequently seen in news reports, environmental campaigns, and government announcements. Unlike general terms for ‘smoke’ or ‘fumes’, ‘尾气’ specifically denotes engine exhaust from motorized transport, not industrial smokestacks or cooking fumes.