What's up 

An excuse for your friends to be dickwad punsters when you just want to hang out.

A-Hey what's up?
B-The sky!! hehehehe
A-Fuck you, Thomas

What's up by j00j00 May 31, 2015

what's up 

A question that means "hi" or "What are you doing"
It can get annoying, but people don't seem to understand that.
The best way to answer is "I think it's the opposite of down" if you are annoyed by this question

"What's up?"

what's up by The Billionth Random Monkey December 15, 2014

What's Up?

1. A casual greeting or conversation starter, somewhat of a rhetorical question.
Usually followed by something like "Not much, you?," "Nothing much," or even answered with a "Hey man, how's it going?"
syn: How's it going? What is new?

2. syn. What can i do for you?, What would you like? What's on your mind?

1. Person #1: Hey There! What's up?
Person #2: Oh not much. What's up with you?

2. Person #1: Hey come here for a second, I have to ask you something.
Person #2: Ok, what's up?

What's Up? by GangstaRL December 28, 2005

what's up 

see also: whazzup, whassup, whasabi!!, etc.
1. Hi
2. Wtf is wrong with you??

It's probably originated from the late 20th century, when people were astounded with the sky. The only thing that they would reply was "nothing"

Probably the first term to the decline of western civilization

1. Person 1: What's up?
Person 2: "Nothing" (most common response, maybe 99% of people say that)

2. Person 1: What's up?
Person: "The sky" (smart alleck answer: also: "the ceiling" or, "da roof")

what's up by FunkdogdiggityJ-izzle mister blah?? i'm in the house yo, so holla at me after mah home fries get back! word! April 7, 2004

what's up 

Possibly derived from "what's the update." Extremely overused, almost exclusively by America's youth.
Sometimes I wonder why people always ask each other the same question over and over again, when answer is always "nothing." Are we really that dull?

Mike: What's up?
Matthew: Nothing. If you ask me again I'll roast you.

what's up by Renaissance Woman 4 u January 8, 2005

What's up?

There are many definitions for this.

1. The opposite of down.
2. The sky
3. The clouds
4. The sun

5. Space

If you want to be boring, you can just say:

1. Good
2. Bad
3. Okay

Me: Hi

Mom: What's up?

Me: The opposite of down.

What's up? by OofBanana March 19, 2019

What's Up 

An extremely annoying phrase used by people who have never heard of "hello." Usually people ask this when they are bored, expecting the person they're asking to entertain them.

Guy: what's up?
other guy: *sigh* stop trying to make me entertain you.

What's Up by The Ironic Geek September 27, 2015