Definitions of complaint:

• noun:   (civil law) the first pleading of the plaintiff setting out the facts on which the claim for relief is based
• noun:   an expression of grievance or resentment
• noun:   (formerly) a loud cry (or repeated cries) of pain or rage or sorrow
• noun:   (criminal law) a pleading describing some wrong or offense
• noun:   an often persistent bodily disorder or disease; a cause for complaining