When someone acts extremely lame. Where someone is really lame and it's sillier than a regular dinosaur on their silliest behaviour, resembling a "T-Rex".
Dude bro, you're so lameosaurus rex... that joke wasn't even funny.
A dinosaur of a status of rolling on the floor laughing
"Oh my god that is so funny! Roflsaurus rex!
A female with such large tits that they are compared to the size of a prehistoric creature
Inbetweeners:
"Cor, Check out the Juggersaurus Rex"
"Shit, and it's Carly"
the greatest of all the ginasaurs.
John, quit being a vagasaurus rex, and go get that bitches number. FAG!
Head coach of the New York Jets. Also a notorious big mouth who tends only to talk the talk and almost never walks the walk. While he has turned the team around, he still acts like he is the greatest coach who ever lived (when in reality people might give that title to Vince Lombardi, Mike Ditka, or Tom Landry). One can only hope he'll get his act together next season if it comes around (all signs point to probably not).
Guy #1: Man that guy is such a Rex Ryan!
Guy #2: I know, he's always running his damn mouth when he shouldn't.
n.
1. Someone or something that performs above all expectations; total achievement in a time of need.
2. A supernatural being that emerges from a clutch performance.
Kevin stopped the hockey puck with his face! What a Clutchasaurus Rex!
Someone who is being a real big pussy.
Dude, stop being a vagisaurus rex.