adverb taking the 'to' particle, adverb, noun or participle which takes 'suru'
feeling refreshed; feeling relieved
Describes a clean, clear, or relieved feeling, often after something bothersome is gone. Used adverbially with と or as a する verb.
試験が終わってせいせいした。
I felt relieved after the exam was over.
彼はせいせいした顔
He went home with a refreshed look on his face.