A blunder is a careless or foolish mistake, usually one that could have been avoided with more attention or thought. When a chess player makes a blunder, they might accidentally move their queen into danger and lose it completely. When a soccer goalie blunders, they might misjudge an easy shot and let the other team score.

Blunders stand out because they're bigger than ordinary mistakes. Forgetting one answer on a quiz is a mistake, but leaving an entire page blank because you didn't notice is a blunder. The word carries a sense that someone should have known better or wasn't paying enough attention at a crucial moment.

People blunder in all sorts of ways. A student might blunder by erasing their correct answer and changing it to a wrong one. A cook might blunder by adding salt instead of sugar to a cake recipe. A politician might blunder by saying something embarrassing that gets reported in the news.

The word can also be a verb: you can blunder through a presentation when you're unprepared, or blunder into a surprise party by walking into the wrong room. Everyone blunders sometimes, and the important thing is to notice, learn, and try again.