tyrant [ME] In English a tyrant has always been a cruel and oppressive ruler, but in ancient Greece, where the word comes from, this was not originally the case. In the 6th and 7th centuries bc a tyrant, or turannos, was simply a man who seized power unlawfully. The tyrannosaurus is the ‘tyrant lizard’. The fossilized remains of this large carnivorous dinosaur were found in North America at the beginning of the 20th century, and the palaeontologist H. F. Osborn gave it the modern Latin name Tyrannosaurus in 1905, taking it from Greek turannos ‘tyrant’ and sauros ‘lizard’. The full name, Tyrannosaurus rex, adds Latin rex ‘king’.