白(しら)けるto be dampened (of the mood, interest, etc.), to be spoiled (e.g. of the atmosphere), to become subdued, to turn sour, to become unamused, to become bored, to become apathetic, to turn white, to fade (to white), to grow light (at dawn)

辞書の定義

一段動詞, 自動詞
1. 1.
  EN to be dampened (of the mood, interest, etc.), to be spoiled (e.g. of the atmosphere), to become subdued, to turn sour, to become unamused, to become bored, to become apathetic
2. 2.
  EN to turn white, to fade (to white), to grow light (at dawn)