1. A deranged state of mind, usually occuring after one has smoked crack, in which one is completely devoid of the principles of logic. Incoherence; insanity; irrationality.
2. The use of nonsensical lies to hustle people for money to support their crack addiction.
My Dad uses crack logic when trying to persuade me to give him money. "I need some money for food! Are you going to let your father die of starvation?" When I bring him several bags of groceries he gets mad because I didn't bring him money with which to buy crack.