The ease with which he had knocked it to pieces disconcerted him somewhat, and to guard against that danger he set to work again, fixing bars of iron on the inside until he was satisfied with its strength; and then, not caring to try any more experiments with it, he passed it and adopted it as a helmet of the most perfect construction.
Don Quixote, disconcerted and in confusion at her appearance, huddled himself up and well-nigh covered himself altogether with the sheets and counterpane of the bed, tongue-tied, and unable to offer her any civility.
There are no more uses of "disconcerting" in the book.
Show samples from other sources
It was disconcerting to realize the experts don’t really understand what is going on either.
Changing teachers in the middle of the semester was disconcerting.