Used as a substitute for yes. Originated from "yes" spelt backwards: "sey" and also has a similar pronounciation to that of the Spanish word for yes: "si".
"So, you wanna come get high?"
A word that is used in time of stokerage (see 'stokerage')!
*Guy sees a dude do an awsome reverse air (bodyboarding move)* "SEYYY!!!!