An onomatopoeic adverb meaning 'briefly' or 'glancingly' — used for a quick look or a fleeting occurrence (e.g., 'glance at' or 'hear something in passing').
廊下で友達の姿をちらっと見かけた。
I caught a glimpse of my friend in the hallway.
彼女はちらっと時計を見て、急いで部屋を出た。
She glanced at her watch briefly and hurried out of the room.
会話の中でちらっと話題に出た程度だ。
It only came up briefly in the conversation.