Bum rush actually was taken from older English jail terminology of when men gang rape a fellow prisoner. This term most likely predates by many decades most of the previous entry's.
Aye, the new guy got bum rushed last night and he was mighty fineone he was.
The act of stealing items from a merchant or street vendor with many people simultaneously running up, grabbing whatever they can and then running off. It has to be done together so that the merchant doesn't know who to try and stop.
I helped bumrush the fake Louis Vuitton stand at the swap meet today with about 14 other people.