do

Hairstyle, short for hairdo. (Mainly 80's slang)

when it started to rain my do got ruined.

Do

To engage in sexual intercourse.

Hey honey, wanna do it?

Doing?

Basically the short hand formed of "What are you Doing?" Can be used as a text, in person, on the phone, on Instant Messaging, basically anyway you want.

Guy to Friend at a bar: Doing?
Friend: Drinking, then going to hit on that girl over there.

Doing'

Visiting or going to. Popular amongst the feminine population

Oh Jem, We're doing the gym tomorrow!

Will Do

The response to a request, favour, or order. When you really want to say leave me alone Fucktard!

Me: Can you return the $50 I gave you?
You: Will do!

DoS

Denial of Service.

Hitting some server with so many requests that it crashes and/or legitimate requests can't get through.

Confusion possible when used as a verb as in "DoSsing a pron site" ("pron" here is intentional).

do

Most often this means sexual intercourse, but sometimes it can refer to offing someone, killing them in other words.