So, 'stop being mardy' is rather more effective in some people's speech than 'stop complaining'.

所以在讲话中用stop being mardy(别再怨声载道了！)要比用stop complaining语气更强。

It's an adjective - 'you mardy cow! ', for instance, somebody might say - quite a strong adjective really.

Mardy是个形容词, 例如我们可以说, “You mardy cow! ”——可以听出，mardy是个感情色彩很强的形容词。