1
deeply;keenly;severely;completely;utterly
彼は、自分の不幸をつくづく考えた。
He brooded over his misfortunes.
2
intently;carefully;closely;attentively
Other forms
熟熟 【つくづく】 (rarely used kanji form) · 熟々 【つくづく】 (rarely used kanji form)