expression, na-adjective
jam-packed; teeming; heaving with people
Idiomatic simile describing a place so crowded that people are packed together like potatoes being washed in a tub. Often used with 混雑する or 混んでいる.
夏の海水浴場は芋を洗うような混雑だった。
The beach in summer was jam-packed with people.
通勤ラッシュの電車はまさに芋を洗うようだ。
The rush-hour train is exactly like a can of sardines.