expression · occurring in a wild, chaotic, or reckless manner without restraint, often used to describe heavy rain or wind

外面下着没头没脸的大雨，根本看不清前方的路。

expression · directed at someone all over their body or without regard for specific parts, typically used for hitting or scolding

他抓住那人的衣领，没头没脸地打了一顿。