Never taught, never trained — having learned whatever you know on your own, without a teacher. A tutor is a private teacher, so untutored literally means 'un-teachered'. It is most often used about a skill or an ability that someone has naturally: an untutored singer, untutored talent, an untutored painter whose work still moves people. Used this way it can be admiring — the person is good without any training, which is remarkable. But it has a second, cooler use, especially in the phrase 'to the untutored eye' or 'the untutored ear': meaning the eye or ear of someone who has not been trained to notice the difference. 'To the untutored eye, the copy looks exactly like the original.' There is no insult in it — it simply means 'not trained in this particular thing', and any of us are untutored in most subjects. It is a formal, slightly old-fashioned word, and it usually goes in front of a noun rather than after 'is'.

未受過（正規）訓練的、自學的；（眼光、耳朵）外行的、沒受過訓練的