To disconcert someone is to throw them a little off balance: they feel slightly confused, embarrassed, or worried, often because the moment was not what they had arranged in their head. A long look, a blunt question, a silence, or a small plan that fails can disconcert a person. It is more than a tiny surprise and less than a shock. The word is fairly formal; in casual talk people say throw off, rattle, or catch off guard. You will hear the adjective forms (disconcerted, disconcerting) more often than this verb. Though actually, the old French idea was to undo an arrangement — to take something that was “in concert,” working together, and mess it up. That is why a disconcerted person looks as if their inner plan has come apart.

使困窘、打亂陣腳、使不知所措