An adverb meaning 'without hesitation' or 'without reserve'; used to tell someone they may act freely or speak frankly.
遠慮なくご意見をお聞かせください。
Please feel free to tell me your opinion.
どうぞ遠慮なくお使いください。
Please feel free to use it.
遠慮なく質問して構いませんよ。
You may ask questions without hesitation.