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to swing; to sway; to shake; to tremble
to waver; to feel shaken; to become unstable
夜風に吹かれてろうそくの小さな炎がゆっくり揺らいだ。
The candle flame flickered in the wind.
反対意見を聞いて彼の固い決意が次第に揺らぎ始めた。
His resolve began to waver.
強い地震の揺れで高層ビルが大きく揺らいで怖かった。
The building swayed greatly in the earthquake.