Top definition
When the girl you are out with won’t give up the pussy for sex but realizes that she has given you a horrendous case of blue balls and agrees to give you relief with a merciful hand job milking you free of that aching nut.

A common occurrence with a “good girl”’and on first dates. Very rarely happens when you are out with a thot or slut.
My first date with Rachel ended with a mercy milk. I was blue balling real bad.
via giphy
by Eaton Holgoode June 04, 2018
Get the mug
Get a Mercy Milk mug for your fish Yasemin.