[ léi shēng dà ， yǔ diǎn xiǎo ]

比喻做起事来声势造得很大，实际行动却很少。

宋·释道原《景德传灯录》卷二十八:“雷声甚大，雨点全无。”

his bite is worse than his bark; action speaks louder than words; loud thunder, but only tiny drops of rain (idiom); a lot of talk, but no action