Well, for me an actor is someone who learned it and not someone who only made a small cameo.

But I looked into the dictionary and you don't have two different words. We have two words in German language. One is "Darsteller" who is someone who is acting (for example in a daily soap opera) but without any education and "Schauspieler" for real actors with an education at a drama school or someone with long-time experiences and "learning by doing" like Jodie Foster for example who never had acting lessons. Both are acting but one of them has learned it and the other one is casted from a casting company but doesn't have any education and experiences.