In a manner that is characteristic of a child; immaturely.

बच्चे जैसा; बचकाना

English Usage: He acted childishly during the meeting, throwing tantrums when he didn't get his way.

Hindi Usage: उसने बैठक के दौरान बच्चे जैसा बर्ताव किया, जब उसे अपनी मनमानी नहीं मिली तो उसने गुस्सा कर लिया।