In the BBC TV series Merlin, the dragon terms Merlin a Warlock. The evidence is that this is generally considered a negative or evil term, so why is he called it? Surely it would be better to call him a wizard?
My only thoughts are that his specific powers, or possibly his position as dragon-lord make a difference, but this does not seem to be the case according to everything I can find on warlocks.
He is at least trying to be a good wizard, and the dragon in particular does not have a problem with him - I could have understood Uther using the term, or even Arthur ( although everyone else just says they "have magic" ).