"Dank" is synonymous with kind bud, and is often used interchangeably with "sinsemilla," although dank is more of a loaded word. The term refers to the pungent, fresh, "dank" smell of high-grade (often moist), seedless (sinsemilla) marijuana.
Bro, I picked up some medicine at the Co-op the other day that was just dank.
really potent weed, produced by proper slow drying of harvested plant material, usually requiring curing (putting plant material in paper bag, folding over top, placing that bag in another bag. Thus reducing air and light contact on said plant materials, so when you go to retrieve some of said plant materials, it is still moist, green and sticky because the resin glands are still intact and 'sweating'.
usually can only be found on or near a High School (go on, Im sure your son would love to hook you up with some digity dank.