expression, godan verb (-ku)
jerk off; masturbate
Colloquial, vulgar expression for male masturbation. Used casually among close friends or in informal contexts.
昨日、久しぶりにマスをかいた。
Yesterday, I jerked off for the first time in a while.
More clinical and neutral term for masturbation, not limited to males.
Another vulgar slang for male masturbation, often used in 2ch or otaku culture.
The origin is uncertain. マス may derive from マスターベーション (masturbation) or from a slang term for semen. The verb かく (掻く) means 'to scratch' or 'to stroke', fitting the action.