The distinct stench that smothers items from donation shops or consignment stores. Junk funk often is a smelly mixture of stale tobacco, mildew, animal dander, and other odors that accumulate in storage spaces or dirty places along with hair and unnamed "items" or stains. It's typically impossible to fully remove junk funk from the item which it inhabits.
Tom: Hey, check out this cool leather jacket I just got from Goodwill. Only six dollars.