This is a word rooted in the many meanings for kush (refer wiki's Kush, kush
) that have arisen through history. Kushers are objects that mean different things to different people. Objects deemed as kushers usually provide happyness ('Khush' means 'Happy' in Hindi).
Objects may be Psychadelic (originating from the fact that kush is a very potent strand of marijuana). They may be violent (in a funny way). They could be awe inspiring or just interesting to the individual that deems the object a kusher.