A myocardial infarction brought on by the act of simultaneously hitting cocaine and heroin (commonly known as a speedball). Rhyme for effect.
My buddy John was hitting the speedballs one after the over, then all of a sudden, he collapsed to the ground, clutching his chest. It was a smack crack heart attack.
Billy: Hey Dad! Guess what I got with my 15 dollars of allowance?!
Dad: What did ya get, sport?!
Billy: I got a black hooker to give me the crack sack down on 5th and Main in her '94 civic!
Dad: Last time I did that, the hooker got half way through the line and tweaked out and bit into my sack and I got half a line of coke directly to my balls! God I love your mother...
Several meanings. Most commonly refered to as one who is doing stupid things, as in a person who is so out of it, they are trying to smack crack into their skin directly. Also, can be used as a term of endearment, or torment depending on the person.
don't taunt the bullwith thatred cape, you crack smacker.
or,
that was so sweet of you to buy me those flowers you are such a crack smacker