An amalgamation between a "munter" (see munter) and a mattress.
Usually a largeindividual that should know their limits, and comedic for all the wrong reasons.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.