The Art of gifting an item to a friend or relative, by sneaking into their house and placing said item unwrapped among their personal belongings, in such a way they have no clue who gifted the item to them or where it came from. also can be referred to as Ghost Gifting.
I found a Venus statue in my room, I believe someonehas been ninja gifting me while i was at work.
the act of jacking off in public areas, like in the back of a classroom, or in the bathroom while other people are trying to shit and mind their own business.