风吹草动

風吹草動
fēngchuīcǎodòng
  1. lit. grass stirring in the wind (idiom)
  2. fig. the slightest whiff of trouble

CEDICT

tiny movements and changes

Wiktionary

比喻轻微的动静变化。

重編國語辭典

轻微的动静变化

維基詞典

Entry Composition

1 风吹 fēngchuī wind blow
2 草动 cǎodòng movement of a grass; small movement or change