Stealthily or secretly; doing something quietly so that others do not notice. Similar to こっそり and こそこそ.
彼女は誰にも知られないようにこそっと家を出た。
She left the house quietly so that no one would know.
誕生日の朝、私はプレゼントを枕元にこそっと置いた。
On the birthday morning, I secretly put the present by the pillow.
試験中に友達にこそっとメモを渡すのはやめなさい。
Don't pass notes to your friend stealthily during the exam.
夜中にこそっと台所でお菓子を食べた。
I sneaked into the kitchen in the middle of the night and ate some snacks.