What is the symbolic meaning behind an 8 ball tattoo?

I heard my sister-in-law today telling someone that her ex-boyfriend got a flaming 8-ball on his forearm and that it's a symbol for cocaine. It is not necessarily a symbol for cocaine but since her ex was a coke user it was a symbol of coke for himself, hence the 8-ball(the pool ball and an 8ball of coke). Virtually no one else would look at this tattoo and assume that he is a coke user; they may think he likes to play pool.