A phrase typically, but not always, used in conversation; can also be used in response to a fact, or its opposite, in media; the appropriate response to any sentence including any variation of the descriptor 'bullshit', when the word 'shit' is being used as a verb, and the preceding perceived assertion or premise reflects a known truth or fact. Also used as its reverse as a prank, to generate belief in something patently false and normally unbelievable.
You: Idaho is a state in the USA? You're shitting me!
Them: I shit you not! It's a state!
You: I thought it was an invention of the corn industry.
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.