dirty trick; underhanded method
Refers to a dishonest, unfair, or sneaky way of doing something. Often used in contexts of competition, business, or personal dealings.
He got the contract by a dirty trick.
I can't forgive such an underhanded method.
Standard kanji-kana mixed spelling.
Kana spelling of the adjective part; sometimes used for emphasis or in informal writing.
Compound of 汚い (dirty, unclean) and やり方 (way of doing, method). The figurative use of 汚い for 'underhanded' is well-established in Japanese.