When one sneaks into a bedroom or an area where someone is sleeping. You then proceed to masterbate(or rub one out) on the sleeping persons face and quickly sneaking back out before that person awakes
I gave Sally the sneaky bandit while she slept in the next room
When at a party and theres a douche bag of extreme quality walking around hitting on all the girls and getting way to drunk. Then after the douche bag has passed out someone goes over and masterbates, ejaculating into the douch bags boxers making him think hes had a wet dream. That is a Sneaky-bandit
Timmy - So dude we were at Johnny B Goods party last night and this douche bag was hitting on my girl so once he passed out we totally gave him a Sneaky-bandit!!!!
Otis - Dude.....gross