An acronym meaning "Minors, do not interact," telling people under the age of 18 to not interact (like, comment, repost) with a post and/or to not interact with the account (message, follow).
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.