不约而同

bù yuē ér tóng

as if by prior agreement

Character by character

不bù
not

约yuē
arranged

而ér
yet

同tóng
the same

大家不约而同地笑了起来。

Everyone burst out laughing at the same time.

Tone: neutral.

Usually 不约而同地 + verb, for a spontaneous shared reaction.

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