Although the word "magician" doesn't appear in any of the Potter books, it does appear in a Pottermore article about Vernon and Petunia Dursley:
Petunia did not want Lily as a bridesmaid, because she was tired of
being overshadowed; Lily was hurt. Vernon refused to speak to James at
the reception, but described him, within James’ earshot, as ‘some kind
of amateur magician’.
This obviously could be considered an insult within the wizarding world.
Note that the word "illusionist" is also conspicuously absent.
Interestingly, Alan Rickman describes his character, Snape as a "black Magician" in an interview with Unreel
I think at heart Snape is basically quite an insecure person, he's
always longing to be something else that people will really respect
like a black magician not just a school master. That's why he envies
the more popular and successful boys like Harry. He does have his
positive side though even though Harry's a thorn in his side he
doesn't let it worry him too much.