A period of time spent doing nothing that isnt completely silly, hopefully bizarre & enormously fun! Usually undertaken when under the influence of alcohol or drugs or both.

Best enjoyed after (in fact it only really qualifies as 'a mad one' after) at least one night's sleep deprivation.

(It is also worth noting that 'a mad one' is normally accompanied by almost continuous, totally sincere but basically pointless, apologies to anyone nearby who is halfway normal)
"Sorry mate, don't mind us ..we're on a mad one"

"I know I am talking shit mate, sorry, I've been on a bit of a mad one"
by The Insomnianiac June 28, 2005
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English phrase used to describe the state an individual or party of people are in when they have ingested a significant amount of any one or combination of intoxicating substances and have aspirations of engaging in sexual relations and/or violent conflict with other rindividuals
I am on the mad one sir
by Tom Rowsell May 30, 2007
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To be on a mad one=to be going crazily angry at no apparent provocation
Seán: Can I have a pencil please Miss?
Miss Griffin: No Seán, go and buy your own f*cking pencils, you little b*ll*cks.

Seán(to friends):Jesus lads, don't go near Griffin today, she's on a mad one.
by Jamachine May 8, 2007
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someone who acts extremly crazy for attention
person 1:Your mum's a mad one

person 2:get out
by 250107 March 16, 2022
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he said: Do you honestly think you're fucking funny, fucking with my friends? Seriously, you're a fucking ugly little cunt mate, and if I ever see you i'm gunna slit your fucking face wide open yeh? You're a fucking angry little fucking spastic.
that one mad Australian guy in cod says toxic shit
by wsdfibg;ewrgewiluyy August 1, 2023
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