In a sneaky or secretive manner; doing something on the sly so that others do not notice.
子供たちは夜にこそこそと起き出して、リビングへ行った。
The children sneaked out of bed at night and went to the living room.
彼は上司に見つからないようにこそこそと書類を机から持ち出した。
He secretly took the documents from the desk so his boss wouldn't notice.
こそこそ話すのはやめてください。会議中ははっきり話しましょう。
Please stop whispering secretly. Speak clearly during the meeting.