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unwillingly; reluctantly; grudgingly
shaking one's head in refusal (like a child)
いやいや承諾したが結果的には良い経験になった。
I agreed reluctantly, but it turned out to be a good experience.
いやいや始めたプロジェクトが成功した。
The project I started reluctantly was successful.
いやいや従うよりも自分から進んで動いた方がいい。
It is better to act on your own initiative than to comply reluctantly.