When one usually with a group of friends smokes marijuana. Refers to association of reggae and musician Bob Marley with marijuana. "Tickets" to the concert can be any marijuana related paraphernalia including, marijuana itself, or what is used to smoke it. Reggae music is optional.
Jack: Hey Mark you want to go to a Bob Marley Concert?
Mark: Yup, I've got my ticket right here (pulls out bag of weed)