Teeming with people; packed so tightly that people jostle one another (used like 'like potatoes being washed' to describe crowds).
休日の駅は芋を洗うような混雑で、改札を通るのに時間がかかった。
The station was so crowded on the holiday that it took time to pass through the ticket gate.
バーゲン初日のデパートは芋を洗うようだった。
The department store on the first day of the sale was packed.
祭りの屋台通りは芋を洗うように人があふれていた。
The festival's food stall street was overflowing with people.