Refers to the act of groping or sexual molestation, especially in public places like trains. Often used in legal and news contexts.
Groping is a crime.
Groping on trains has become a problem.
痴漢 refers to the person who commits groping, while 痴漢行為 refers to the act itself.
セクハラ (sexual harassment) is a broader term covering verbal and non-physical harassment, while 痴漢行為 specifically involves unwanted physical touching.
Compound of 痴漢 (chikan, 'molester') and 行為 (kōi, 'act'). The term 痴漢 itself is composed of 痴 ('foolish') and 漢 ('man'), originally meaning a foolish man, but its modern usage is specific to sexual molestation.