Lacking a firm will and easily swayed by circumstances; indecisive and inconsistent.
他做事总是飞蓬乘风，缺乏主见，常常轻易改变自己的决定。
He is always like a tumbleweed riding the wind in his actions, lacking initiative and often easily changing his decisions.
Next Idiom
Lacking a firm will and easily swayed by circumstances; indecisive and inconsistent.