smog
n.a thick, dirty type of air pollution that looks like a mix of smoke and fog. It usually happens in big cities where there are many cars and factories.
n.a form of atmospheric pollution consisting of a mixture of smoke and fog, or chemical fumes. Often results from the interaction of sunlight with industrial emissions and vehicle exhaust.
“The city is covered in thick smog today.”
“Local authorities issued a health warning because the smog was so thick that it reduced visibility on the highway.”
“Heavy industrialization combined with a lack of wind created a persistent layer of smog that hung over the valley for several weeks, prompting calls for stricter emission controls.”
Blend of smoke + fog.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.