A girl or gay male who has sucked so much cock and knows penis so intimately that he/she can easily tell the difference between a blue ribbonwinning penis and sub-par penis.
A portmanteau word combining "connoisseur" (which means someone who is an expert judge in a particular matter) and "Tyrannosaurus Rex" (dinosaur species whose name means "tyrant lizard king" and is known as the angry, carnivorous jerk among dinosaurs that no other dinosaurs liked).
"Connoisseurus Rex", therefore, represents someone who takes connoisseurship to the next level by being a condescending, and at times hostile, douche. Connoisseurus Rexes are typically considered too annoying for actual friendship.
Geez why did he have to rip my head off over the way I did this?
Oh don't worry, he's just being a Connoisseurus Rex.
Have you ever seen that episode of Aqua teen hunger force where they use a ray to enlarge Carl‘s genitals and crabs start crawling out of his shorts? He is NOT a Condom Connoisseur.