The very foul smelling, disgusting fluid that is unfortunately a product of nonstop female masturbation, also known as "Fapping." Fap Juice is most easily detected while temporarily sharing a home with an extremely nasty woman who has a fake online boyfriend,masturbates alot and never takes a shower.
Damn, it smells straight up like FAP JUICE in your sister's room! She must have been FAPPING ALL NIGHT LONG!
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.