Hi,
Yes, the general term was usually "die Kanone", which literally translates as cannon. Modern writers have usually said it equates to "big shot" or "top gun" in today's parlance, but 'ace' is clearly signified. I don't know if there was any official criterion for this (I doubt it), but usually a German pilot had to have ten victories before he would informally be referred to as a "Kanone". For instance, Richthofen jokingly told
Hans Joachim Wolff (after the latter's 4th victory) "Until you get out of those ridiculous single-digits with your victories, you'll never be a 'Kanone'."
Sometime, a high-scoring ace would be called 'eine grosse Kanone', or a great ace.
Greg