This is a word used to describe what you will be doing or did the other night/day. The word west-coastin has been taken from the Knocturnal song ‘Bad Intentions’. I don't give a fuck 'cause I'm just drinkin, smokin, straight west-coastin.
If you have been out the night before drinkin and smokin weed you have been out west-costin.
Person 1: Yo dawg you was mashed last night!!
Person 2: Yeah I know I was straight west-coastin all night.