fug

Fug is an informal English noun describing a thick, stale, and often unpleasantly warm or humid atmosphere in a closed space. It refers to air that feels heavy, stuffy, and hard to breathe, frequently accompanied by odors from sweat, cooking, dampness, or poor ventilation. The phrase in a fug or the fug is commonly used in both American and British English to convey a sense of oppressive stillness or claustrophobic air.

Origins and usage are unclear, but fug is generally regarded as mid-20th-century slang that later spread beyond American English. It is chiefly a colloquial term and appears in everyday speech, journalism, and literature. The related adjective fuggy describes air or environments with this quality.

In discourse, fug is not a technical term but a vivid descriptor of environment and mood. It is often contrasted with notions of fresh air, ventilation, or outdoor air quality. Because of its informal nature, it is more likely to appear in narrative writing, personal accounts, or casual conversation than in formal or scientific writing.

See also: stuffiness, humidity, air quality, miasma.