台Taivo A Taiwan Mandarin dictionary

戴綠帽子

dàilǜmàozi

ㄉㄞˋ ㄌㄩˋ ㄇㄠˋ ˙ㄗ

Simplified 戴绿帽子

1to have been cheated on by one's partner (formerly meant "to be a cuckold", i.e. applied to men only)

Keep 戴綠帽子 and it comes back until you know it.