Complain incessantly is a phrase that describes someone who is constantly voicing their dissatisfaction or displeasure. This can be done in a variety of ways, such as moaning, nagging, and CARP. Moaning is a low, prolonged sound of pain or discontent. Nagging is to persistently and annoyingly ask for something. CARP is to find fault or complain querulously and persistently. All of these words describe someone who is constantly complaining and voicing their displeasure.