dirty trick

Từ điển Oxford Advanced Learner 8th

ˌdirty ˈtrick [dirty trick] BrE NAmE noun
1. usually plural dishonest, secret and often illegal activity by a political group or other organization that is intended to harm the reputation or success of an opponent
•a dirty tricks campaign
2. an unpleasant and dishonest act
•What a dirty trick to play!