adj. metonym. A day spent evading from one's otherwise usual responsibilities (work, school, babysitting etc) with one or more other people, in the pursuit of a more fun activity - typically drinking, vandalism of driveways and other such anti-social behaviour.

Inspired and popularised by Episode 2 Series 1 of the Channel 4 (UK) television show The Inbetweeners.
Me and the boys had an inbetweeners day last Thursday - it was great, we beat all the queues at Thorpe Park.

Dangerous Dave: Wagwan bruv, com'e'go do an inbetweeners day tomorrow.
Sensible Steve: No man, we got a conference call with the Washington office in the afternoon.
Dangerous Dave: Allow that shit man, we'll go Thornton Heath and chirpse some clunge innit.
Sensible Steve: Aight, safe.

Greg did not approve with the group's decision to have an inbetweener day on Thursday. What a bumder.
by shauny fizzle July 15, 2010
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Days that arent good and arent bad, but you still need something.

A day where you are missing something or someone.
"Today is my inbetween day."

"I don't really like inbetween days."

"I really like the cure song, Inbetween Days."
by Nicole Moore February 6, 2008
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When you and your friend's birthday's are five days apart. It is the day that is right in between.
Happy inbetween birthday day!!!!
by Mar W. January 30, 2009
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