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2.
A day off from work or school during which you sort out all your emotional and psychological problems.
Parent: Don't you have a test today?
Student: Yeah, but I'm taking a mental health day. I'll make it up tomorrow.
by starreyes October 14, 2007
 
1.
A quasi-legitimate excuse to take a day off from school or work. Although the person who takes the day off claims he needs it to finish up some work and regain sanity from the rat race, he usually ends up sleeping in, masturbating and accomplishing less than nothing.
J.C. said he took a mental health day to catch up with work and relax, but instead, spent the whole day fantasizing about Jamie.
by Hrach April 17, 2005
 
3.
When you call in sick to work. But you really just want to take a day off and chill out.
Yeah, on Monday I took a mental health day and went on a daycation. It was so relaxing.
by piratemaxx February 15, 2009