The phrase "fast one" can mean trick, deceit, or con. Synonyms for this phrase include hoax, scam, fraud, swindle, racket, deceitfulness, treachery, duplicity, double-cross, and betrayal. These words signify an act of dishonesty or an attempt to cheat or deceive someone. Scams and cons are prevalent in various industries, such as finance, online shopping, and telemarketing. It's always important to be cautious and stay alert to red flags that may indicate a possible trick or fraud. Familiarizing yourself with these synonyms for "fast one" can help you identify and avoid potentially dangerous situations.