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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 27, 2005
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