used to refer to women who have very flat asses. their lack of an ass makes it appear as though they just have a butt crack on their backs.

1. (noun) The white or gray film that forms on the inside of a glass dick after smoking crystal meth.

2. (verb) The act of "melting" the aforementioned film off of the glass dick while inhaling the resulting smoke in an attempt to get high after you've smoked all your d.

3. (verb) The action and reaction of recrystalization of crystal meth when melted completely and then cooled.

crack back is crack and ganja mixed