reverse deposit
A covertly communicated intent to make an ATM withdrawal as prerequisite to making an illegal, immoral, or unethical purchase; specifically if stating a more common phrase, "...I need to hit the ATM..." for example, would generate unwelcome interest in the arrangement being made; the interest would come from perhaps an undercover officer, police informant, or NSA/DEA agent randomly eavesdropping.
"I just need to make a reverse deposit, then I'll be right over to play some 8-ball. So rack 'em up."