When you
bum rush someone, it means you ambush them using an unfair combat advantage. A lot of the other definitions list it specifically as charging someone and bodyslamming them into a solid
wall, which is applicable because it's total
bullshit and usually catches the victim off guard. Other examples include (but are not limited to) attacking someone from behind by sprinting at them and landing a tackle, ganging up on someone and beating them to the ground with superior numbers, or hitting someone with a sucker punch while they're distracted fighting someone else. This is also a tactic in the board
game risk, but in this case it consists of plopping down all your armies in
one previously weakly defended country and defeating the surrounding countries (usually defended by only 1 or two armies) by
spam attacking and having your opponent be unfortunate enough to
roll a 1 every goddamn
time and lose half their territories. Smash and grab robberies could be considered another example, as a
mob of people obscure their faces, run into a store, grab
whatever they can, and dash out in the blink of an eye, using their superior numbers to overwhelm store security and staff and to make it harder to uncover an individual suspect's identity. Bum rushing comes from the fact that these tactics are often seen as cheap or low of someone to use, which makes them a
bum for having to use them instead of a fair fight.
Example 1: I almost got killed yesterday. This dude freaking bum rushed me and stole my wallet after pistol whipping me out of nowhere with his
gun.
Example 2: "I've got his legs!
Break both his arms with the bat while guy 3 hits him in the nuts with his golf club!"
Jack thought he had found the ultimate spot to survive in tf2 zombies but his posse was quickly wiped out thanks to the
zombie medics bum rushing them by spamming taunt heals and taunt kills by the doorway until the other medics were able to make a breakthrough and swarm the room.