Just slang for very good weed.
Person 2: Well not with your looser stuff. I've got some kush, let's better smoke THAt if you want to get wasted!
Drgreenthumb: Thats some Master Kush my friend, best you can find outside of the Cannabis Cup.
A high grade strain of marijuana,originating in the Hindu Kush mountain region located in Afghanistan as well as northern parts of Pakistan. The strain has a high THC(tetrahydrocannabinol) concentration, with bushy resinous plants. Witch emit a pungent,sweet odor.