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1, When a person makes plans about doing something with someone else and then the person backs out at the last minute without notifiying the other person.

2, To drop out of university, college or any other educational establishment without a justified reason.
John: Hey, Himbleton invited me to see the new Batman film yesterday but he didn't show up!

Alexander: Oh dude, don't tell me Himbleton Mason'd it again
by Prince Boobs September 12, 2009
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