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(slowly and) carefully; without haste; thoroughly; deliberately; closely; meticulously
問題をじっくり考えてから答えを出した。
I gave an answer after thinking carefully about the problem.
じっくり煮込んだスープはとても美味しい。
Slowly simmered soup is very delicious.
時間をかけてじっくり話し合う必要がある。
We need to take time and discuss thoroughly.