one-blocker

One who looks fantastic from about a block away, but as you get closer to the person, he or she has major flaws; i.e. the beautiful tan skin is baggy or wrinkled, the bleached-blond hair is dry and straw-like, etc. The person is, overall, less hot than originally anticipated.

My neighbor's a one-blocker.

Drunk one

A drunk one is the person that says the most stupid things. They are the type of people who are not really drunk but act like it. They can be very awkward and are the most terrible singers. If you know a drunk one approach it with the greatest caution. You'll never know what they'll do.

Girl: OMG that guy is such a drunk one.

Boy: chill dude you don't want to be labeled as a drunk one.

under-ones

Underwear; undergarments. Typically used as a uni-sex term referring to panties, boxers, briefs, brassieres and similar. The hyphenated spelling is grammatically correct, however alternate spellings may include: underones, under ones.

Her pants were so sheer, you could tell what color her under-ones were.

a bit of a one

A chancer. Someone who pushes the limit of what is acceptable and treads that fine line.

Did you see Tony at the market last weekend? He was flogging hooky DVDs and Blu-Rays.
Yep, he's a bit of a one, that Tony.

It's been one

It's time for action
It been over

It's been "one more time" now it's on sight!

It's been one. I'm done with this

One Fifth

one part of five. 20% of something

"Don't tell me you're about to drink all that?!?"
"Nah G, only one fifth"

one swiper

The rare occurrence of only needing one swipe of toilet paper to completely clean your arse after taking a shite.

Jim: "How did that shite go for ye?"

John: "Great, it was a one swiper"

Jim: "Can't bate them"