noun
dirty old man; creepy middle-aged guy
Derogatory internet slang for a middle-aged man perceived as lecherous, unkempt, or unpleasant. A play on おっさん (middle-aged man) with the kanji 汚 (dirty).
See also: おっさん
電車で隣に座った汚ッサンがずっとこっちを見てて気持ち悪かった。
The creepy old guy sitting next to me on the train kept staring at me and it was gross.
ネットでは、ちょっと嫌な中年男性のことをすぐ汚ッサン呼ばわりする風潮がある。
Online, there's a tendency to immediately label any slightly unpleasant middle-aged man as a 'dirty old man'.