To “Have on” is a term which means, being in the possession of drugs, mainly marijuana. As in having on them.
Guy 1: Does anyone need on? I have some with me right now.

Guy 2: Yeah! Can I have on? What have you got?
by Dento November 25, 2017
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We are ready to start, let's have at it.
by Hoda Man July 23, 2008
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When someone is unwilling to accept the current or proposed state of affairs. Can also be used when someone doesn't believe you're telling them the truth.
Bush thought he'd slip Harriet Miers by on a nod and a wink, but the Busheviks weren't having it.

I told my mom I wasn't the one who put a dent in the car, but she was NOT having it and pressed me to give her the whole story.
by The Grammar Nazi November 5, 2005
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When something is seen as required.
"I didn’t have to add any sugar to my mocha latte."

"What do you mean?"

"I didn’t find its taste bitter and disgusting enough to cause me to add more sugar from the office in order to make it palatable for me."
by nanigansguy May 22, 2017
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(noun) A person who does not possess the necessary credentials in order for them to be successful. Likewise, this person is not able to express qualities of credibility.
The networking teacher said that he could not take the day off because he was a have-not and needed to work towards his certification.
by McCrapper March 25, 2013
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When placing a plate of brownies down infront of his drunk friends, Tom said "have at it boys".

After seeing Sean get punch repeatedly by the opposition in the middle of a maul in a rugby game, Tom grabbed the offender in a full-nelson and positioned him face-first to Sean, saying "have at it".
by Dirty Little Tommy August 4, 2005
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This phrase can mean a lot, perhaps to much. In some circumstances it can be the same as 'have it' but of course 'having it' is somewhat in the present tense.

So perhaps think of 'having it' as a outburst response to having extreme fun, mostly summoned for circumstances of a sexual, drug consuming, party time!
Fucking sweet to the eye balls buddy, I'm having a great time in fact you could say I'm fucking 'Having It' !

I guess I should get my ass in gear, strike up a fattyboombatty and start fucking 'having it'

Shitballs! I heard you had a proper session last night with the local hooksta!
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lol, yeah she was fucking having it.
by dat-ting June 13, 2007
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