Someone who's behavior is so childish, spoiled and annoyingly bratty that that they are king or queen of brats but in dinosaur dimensions. A complete shithead or douche bag.
Paris Hilton, filthy whore, is such a brattysaurus rex for her complete self-absorbtion and disregard for anything important.

Yeah, she is such a brattysaurus rex that she would not not know a charitable cause if it hit her in one of her many anal warts.
by northbeach Scott October 18, 2011
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