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running fast; double time
cantering
doing things in a hurry
電車の発車時刻が迫り駈け足でホームに走った。
With the train's departure time approaching, I ran to the platform at full speed.
駈け足で説明したので分かりにくかったかもしれない。
I explained in a hurry, so it might have been hard to follow.
朝の駈け足訓練が新入生には一番つらい。
Morning double-time drills are the hardest for new students.