expression, ichidan verb
smile a satisfied smile; break into a smile of satisfaction
A literary or slightly formal expression for a smile that shows deep personal satisfaction, often after a success or achievement.
彼は会心の笑みを浮かべて、優勝トロフィーを受け取った。
He smiled a satisfied smile as he received the championship trophy.
難しい
After solving the difficult problem, she broke into a smile of satisfaction.