To grow faint or thin; to fade or weaken gradually (e.g. color, memory, feeling).
子供の頃の記憶がだんだん薄らいでいく。
My memories from childhood gradually fade.
彼の怒りは時間とともに薄らいだ。
His anger faded with time.
明かりが弱まり、部屋の輪郭が薄らいで見えた。
The light dimmed and the outlines in the room looked faint.