An onomatopoetic adverb meaning to glance sharply or stare briefly (often with disapproval or curiosity).
彼は私をじろっと一瞥してから無言で立ち去った。
He gave me a sharp glance and left without a word.
先生が教室に入ると、生徒たちはじろっと彼を見た。
When the teacher entered the classroom, the students glanced at him sharply.
あの店員、じろっと客の服装を見ていたよ。
That clerk gave customers a quick, sharp look at their clothes.