Whip it is a slang often used to refer to process of turning the drug cocaine into crack. The term comes from the fact that dealers have to whip the cocaine with all the other added ingredients in a pot before it turns to crack. For instance, in Solo Lucci's song "Whip It," he raps, I used to stand in the kitchen, and whip it, and whip it, then chop it and flip it. Solo Lucci is essentially saying that he used to cook crack cocaine (whip it), bagged them, then sold them (flip it).
This slang is not to be confused with the slang "Whip It Out."