Slim describes something or someone that is thin or narrow. A slim person has a lean build without much extra weight. A slim book isn't very thick. A slim margin means the difference between two things is small, like winning a race by just one second.

When you describe a person as slim, you're talking about their body shape in a neutral or positive way. It's different from skinny, which can sound too thin, or slender, which often sounds more elegant and graceful.

The word also means “very small” when talking about chances or possibilities. If your odds of winning the lottery are slim, they're tiny but not quite zero. A team facing a much stronger opponent might have only a slim chance of victory. When possibilities narrow down, we say they're slimming: “Our options are slimming as the deadline approaches.”

You might also hear someone say they need to slim down, meaning to lose weight or reduce size. A company might slim down its workforce during tough times, or you might slim down your backpack by removing unnecessary books. In these cases, slim becomes an action, describing the process of making something thinner or smaller.