When you have sex with a girl, then finish on her vagina. Spread the semen over her vagina and leave it to dry. Once it dries, nothing will get in or out of her vagina, leaving it "beaver dammed"
last weekend i beaver dammed my girlfriend, needless to say she was not happy when she realized what i had done.
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"