na-adjective
Describes a person's manner or speech as polished, diplomatic, and free of friction. Often used for someone who handles social situations gracefully.
彼の円転滑脱な対応で、その場は丸く収まった。
His tactful handling of the situation smoothed things over.
na-adjective
Refers to a person who can adjust easily to different roles or circumstances. Less common than the 'tactful' sense.
彼は円転滑脱で、どんな部署でもすぐに馴染める。
He is so adaptable that he fits in quickly in any department.