Someone who is overly concerned with conventional morals and will often kick up a fuss over nothing. Typically, the word is used to describe someone with a petty, mechanical and shallow sense of morality; characterized by dogma and conventionality rather than reason, with no regard for context or nuance.
Person A: Swearing is bad in any context and should be criminalized! Think of the children!
Person B: They're only words. I could think up far more more vulgar things using only plain dictionarywords than the use of any of one swear word. It's a non-issue. You're just being moralistic.
Pompous and judgmental upbraiding of someone according to a rule-book which you probably don't share
Moralistic Labor multiculturalism spokeswoman Michelle Rowland called on the PM to act (on Eric Abetz' use of the term 'Negro'). "It's 2015", she said, "just about every right-minded human recognises that it's a deeply offensive term"
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.