when you wake up on a Monday morning and you really dont want to go to school/work that day so you dont.

of course you could say "Monday Sickness" any day of the week.
John: hey chris, you going to school tomorrow?
Chris: nah, its a Monday. i think im going fake sick
John: ah, going with Monday sickness, eh?
by Adassica1 October 18, 2010
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A feeling experienced by (But not limited to,) high school aged individuals on the first day of every school week (Monday).
Common symptoms include:
Lowered brain functions,
Bad Temper,
Stress,
and an overall feeling of human (Or otherwise) excrement.
*Jimmy wakes up*
*Jimmy sees it's Monday*
*Jimmy goes back to sleep*

Example 2

1: "Dude, I got a 57% on that test last Monday..."
2: "That's Monday Sickness for you..."
by Perchant February 3, 2014
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