Translation guide
The English word "smut" has several distinct meanings. This guide covers the most common uses: soot/dirt, obscene content, and a plant disease. Each meaning requires different Japanese expressions.
To refer to a black, powdery substance from burning, or general grime.
The most direct translation for soot, the black powder from smoke.
煙突に煤がたまっている。
Soot has accumulated in the chimney.
General word for dirt or grime, not specifically soot.
I clean the dirt off the wall.
Literally "black powder"; a descriptive phrase when the exact nature is unclear.
Some kind of black powder is on the floor.
To refer to sexually explicit material, language, or jokes.
The standard legal and formal term for obscenity. Can be used as a noun or adjective.
The magazine was judged to be obscene.
Colloquial term for dirty jokes, sexual humor, or lewd topics. Common in casual conversation.
Abbreviation of "erotic". Used as a prefix or standalone to describe sexual content, often in media.
Loanword for pornography. Used similarly to English.
To refer to a fungal disease of cereal plants that turns grains into black powder.
The English word "smut" for obscene material does not have a single direct equivalent. Using 煤 (soot) to mean pornography would be completely misunderstood. Choose the appropriate term based on context and register.
わいせつ is formal and often used in legal contexts. 下ネタ refers specifically to lewd jokes or conversation topics. エロ is a casual, broad term for anything erotic, similar to "erotic" or "porn" in English.
He always tells dirty jokes.
He secretly keeps porn magazines.
Watch porn on the internet.