To bicker means to argue about small, unimportant things in an annoying, petty way. When siblings bicker over who gets to sit in the front seat or whose turn it is to choose the TV channel, they're having the kind of tiresome back-and-forth argument that goes nowhere and solves nothing.

Bickering is different from a serious disagreement or a productive debate. People who bicker aren't discussing important ideas or trying to understand each other better. They're just sniping at each other over trivial matters, often saying things like “Did not!” “Did too!” “You always...” “No, YOU always...” This kind of quarreling usually annoys everyone around them more than it bothers the people doing it.

Friends might bicker about which game to play at recess. Parents sometimes bicker about small household decisions. Teammates might bicker about minor details of their strategy. The word suggests that the argument is pointless and that both people should probably just drop it and move on. When people are tired, hungry, or stressed, they're more likely to bicker about things that normally wouldn't matter at all.