Bed Back

Having a extremly sore back, due to long periods of time spent in bed, Likely hungover

I have terrible bed back from this weekend.

Back Canal

Another definition for the butt, usually in relation to anal sex as an alternative sex route.

Kyle's girlfriend wouldn't let him do the deed proper, so he had to take the back canal.

Splash back

When you take a heavy shit, and the water splashes back up, soaking your butthole. Usually in reference to an overused port-o-jon.
AKA stank water wash, mud cleanse, poor man's bidet.

There's nothing worse that dropping a duce in a port-o-jon that hasn't been pumped out in weeks, and getting a splash back.

Back walker

Only hating on a team when they are doing good. Opposite of a front runner

Yo Jeff is such a back walker, he only hates the Jets because they are on fire.

Green Backing

Having sex on a pull table, preferably with green felt.

Last New years Eve party, Katie and I were totally green backing in the den!

back in the grip

Just another way to say back in the day.

We used to date her back in the grip.

Cheek Back

To reply with a witty, ignorant or insolent remark following chastisement

Don't you be cheeking me back

Are you cheeking me back

Old Dublin Colloquialism

Verb - To cheek back: "If I tell him to get his own Leap Card he will just cheek me back"
Noun - Cheeker backer: One who cheeks back
Past participle - Chook back: "Here, he just chook me back!"