不约而同 (bù yuē ér tóng)

(idiom) (of two or more people) to take the same action without prior

Character breakdown

不 (bù) · 4 strokes

Pictograph of sepals of a flower. The modern meaning "no" is a phonetic loan.
约 (yāo) · 6 strokes

Simplified form of 約. Phonosemantic compound. 纟 represents the meaning and 勺 represents the sound. Based on the original meaning "bind". The meaning later shifted to "agreement", "restrain", "keep un…
而 (ér) · 6 strokes

Originally a pictograph of a beard, now written as 耏. The current use as a conjunction is a phonetic loan.
同 (tóng) · 6 strokes

Depicts a large object (凡) like a shoulder carriage that requires the cooperation of multiple people working together to carry.

大家不约而同地鼓起了掌。
to agree by chance (idiom); taking the same action without prior consultation
dà jiā bù yuē ér tóng dì gǔ qǐ le zhǎng 。