Thousands and tens of thousands; a very large number of people or things.
形容数量很多。
老舍《神拳》第二幕做假事骗得了几个人，骗不了成千上万的人。”
There were thousands and thousands of people at the concert.
Learn the next connected idiom: 成千上万 (chéng qiān shàng wàn) → 万无一失 (wàn wú yī shī)
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