dirty tricks
noun [ plural ] uk/ˌdɜː.ti ˈtrɪks/ us/ˌdɝː.t̬i ˈtrɪks/
花招，猫腻，非正当手段
dishonest activities intended to harm someone you are competing against
The airline was accused of a dirty tricks campaign against its main rival. 这家航空公司受到指控，称其对主要竞争对手使用了不正当手段。