To outdo means to do something better than someone else, or to surpass your own previous performance. When you outdo your classmate in a spelling bee, you spell more words correctly than they do. When you outdo yourself on a science project, you create something even better than your last one.

The word carries a sense of competition or comparison. A chef might try to outdo a rival restaurant's famous dessert by creating something even more delicious. Two friends might playfully try to outdo each other by telling funny stories, each attempting to get bigger laughs than the last. Athletes constantly work to outdo their personal best times or scores.

You can outdo others or outdo yourself. When runners say they outdid themselves in a race, they mean they performed better than they expected to. When siblings try to outdo each other decorating holiday cookies, they're competing to make the most impressive designs.

The phrase not to be outdone describes refusing to let someone do better than you. If your friend scores 95 on a test and you score 98, not to be outdone, your friend might study even harder for the next one. It's the feeling of wanting to match or exceed what others accomplish, which can push everyone to achieve more than they thought possible.