playing music that has alot of bass.

when yo trunk knockin hard

an equivalent of dope, awesome, delicious. Usually used for food, a dish can be "slappin" like it's so good that if someone disputes its awesome godliness they are in for a slappin.
Can also be used in the form of a verb to describe something's slappy awesomeness.

When one plays music with a lot of bass and slang, roles down the windows, and turns the speakers on blast so all the BITCHES can hear.

Turning up a listening device extrememly loud

reference to a cool item of clothing, somthing that someone has done that is particularly sound, or anything you want it to mean. it comes from the BENglo-Saxon word 'Slah-pin' which means "cradle of the dusty rat".

usually meaning good or delicious