It is a term used to tell people not to be pussies and try that reef. A play on words of the famous song Don't Fear The Reaper by the Blue Oyster Cult.
Bud: Your hit.
Pussy: No I don't do that stuff, I'm good.
Bud: Dude, don't fear the reefer, just do it.
Pussy: Okay, since your calling me a pussy.
7 de জানুয়ারি de 2011