derives from the separate definitions
1. backyard; slang for the posterior portion of the human body; substitutes for "bum", "butt", and "ass"
2. bandit; a thief, someone who steals, then rides away, is usually very ruff
they travel in varying numbers be very cautious if you spot one, although it they are very hard to spot because they take any shape and form.
best advise is to run and dont hide with your bum sticking up
oh no our neighbor andrew is getting done over by the backyard bandits again!...
oh wow he kinda looks like hes enjoying it this time
Eliza you backyard bandit get out of there!
jenna is walking like she dating a backyard bandit, what did she do last night?