A combination of a rooster and a dragon or snake.
A cockatrice went on a rampage in the Triwizard Tournament of 1792(GF15).
The legendary creature called the cockatrice is actually almost a twin of the basilisk. Some of the characteristics of the basilisk in the Potter books are actually those of the cockatrice, such as the ability to turn people into stone with a glance. Some medieval bestiaries say that the weasel is the only animal which is immune to its petrifying stare. (The Lexicon page 64).
This is a creature which Rowling did not invent