The girl you pick up at a bar only because you're with another girl who is exceptionally hot. Her hotness is effectively your wingman and your proximity to this babe is what helps get you laid by other women. This is similar to a contact high where being near tokers is all you need to get stoned.
Dude #1: I brought this chick home from the bar last night. We totally hooked up.
Dude #2: Were you with that hot friend of yours from college that you used to date?
Dude #1: Totally, and the chick at the bar came over to talk to me. I didn't even open up the set.
Dude #2: Wicked, bro! You straight pulled some contact ass outta that place. We should party with your hot friend more often.
What a grenade says to cut you off from taking her home, typically in a bar scenario, so she feels better about herself, even though she's a grenade and will never get laid with this fruitless tactic. Smarter women will trap you in a lie or convince you to say something off-putting to weed out the clowns rather than leaning on the never clever Just Say No method learned from the D.A.R.E. program taught to them in elementary school. No means no can also be used as an adjective to describe grenades of this type, for example as a no-means-no grenade instead of a supergrenade or slutty grenade. It can also be used to warn your bros by loudly exclaiming to your fellow buddies "No means no, bro!" while in the company of women or while your best friend is attempting to take one home.
Dude: Let's go back to my place.
Chick: No means no, sir.
Dude: Whatever, grenade...