What does a mad one mean?

a mad one meaning in Urban Dictionary

a period invested performing absolutely nothing that isnt entirely absurd, hopefully bizarre & extremely fun! frequently undertaken when under the influence of alcoholic beverages or drugs or both. Best enjoyed after (in reality it only really qualifies as 'a mad one' after) one night's sleep starvation. (additionally it is well worth noting that 'a mad one' is normally combined with virtually continuous, completely sincere but essentially useless, apologies to anyone nearby who's halfway typical)