Foolish means lacking good sense or judgment. When someone does something foolish, they act without thinking through the consequences, ignore obvious facts, or make choices that almost anyone could see won’t work out well.

A foolish decision might be spending your entire allowance on candy the day you get it, leaving nothing for the book fair you’ve been excited about all week. It would be foolish to ignore storm warnings and go sailing anyway, or to procrastinate on a big project until the night before it’s due.

The word suggests behavior that ignores what you already know or what others have warned you about. Everyone makes mistakes, but foolish behavior involves disregarding clear information or advice. If you touch a hot stove once, that’s an accident. If you keep touching it after you know it burns, that’s foolish.

Someone who frequently acts without thinking might be called a fool, though that’s an unkind thing to call someone. You might feel foolish after realizing you made an obvious error, like searching everywhere for your glasses when they were on your head the whole time. That embarrassed feeling is what we mean when we say, “I felt so foolish.”