When you are having sexual activity with your partner - and you're running late for something, so once you've ejaculated, you quickly leave, so you can get to where you need to be.
"I was running late for the board meeting yesterday, but Mandy really wanted it, so I fucked her from behind, squirted my load all over her ass then quickly left"
"You mean you had to cum and go?"
"Yeah - exactly"
the act of ding-dong ditching a house while masturbating, cuming on them, and casually walking away.
Jonny just just did a cum and go to the mayor!
When you are invited into a persons bed for some sexual adventures and after you cum you go. This can also be used as a pick-up line when your intentions are to only have sex.
"I pulled a cum-and-go with that ho." or "I made him cum-and-go."
Pick-up line version: "Hello. You're hot! Would you like to cum-and-go?"