Taru adjective, Adverb taking the 'to' particle
quiet; calm; leisurely; composed
飛行機は頭上をゆうゆうと飛んで行った。The airplane sailed over our heads. Adverb taking the 'to' particle, Adverb (fukushi)
easily; comfortably; without difficulty
Taru adjective, Adverb taking the 'to' particle
distant; far-off; boundless; endless; eternal
Also written 悠悠【ゆうゆう】