The term CARP is related to negative behavior, as all of the crossword solutions are words that describe complaining, criticizing, and nagging. GROUCH (6 letters) is a synonym for grumpy or irritable, HENPECK (7 letters) means to scold or NAG someone, DISAPPROVE (10 letters) is to not accept or agree with something, FUSS (4 letters) is to COMPLAIN or make a FUSS about something, CRITICIZE (9 letters) is to express disapproval of someone or something, PAN (3 letters) is to criticize harshly, BOTHER (6 letters) is to annoy or disturb someone, CENSURE (7 letters) is to express strong disapproval of someone or something, FISH (4 letters) is an aquatic animal, KOI (3 letters) is a type of FISH, NAG (3 letters) is to persistently ask someone to do something, COMPLAIN (8 letters) is to express dissatisfaction or annoyance, CAVIL (5 letters) is to raise trivial objections, RAIL (4 letters) is to criticize harshly, GRIPE (5 letters) is to COMPLAIN, WHINE (5 letters) is to COMPLAIN in a high-pitched voice, KVETCH (6 letters) is to COMPLAIN or WHINE, NIGGLE (6 letters) is to find fault over small matters, QUIBBLE (7 letters) is to argue about insignificant details, and QUIBBLEANDCAVIL (15 letters) is to argue about trivial matters.