When a person (normally a Regan) completely modifies/ changes a story or series of events with their self destructive narcissistic personality, making it completely and utterly unbelievable.
I was walking my dog yesterday and sore a rainbow.
The Reganified version would be something like: I was walking my unicorn yesterday and there was a shower of rainbows, then a magic carpet appeared and I went for a ride with all my new unicorn rainbow friends. It was totally awesome, then we had ice cream and I was totally tripping balls.
To display narcissistic or extreme self centred behaviour with no grip on reality.
Yesterday my unicorn stopped producing rainbows and all day I had to listen to Paul get more and more reganified about how he was being left out and how it was deliberate.