Cool describes something that's a little bit cold, but not very cold. You might have a light jacket for cool weather or prefer to drink cool water instead of ice-cold water.

Cool can also mean impressively calm, confident, or stylish. When you stay cool during a difficult moment, like missing an easy shot in basketball, you keep your composure instead of getting upset or flustered. A person who acts cool under pressure doesn't panic when things go wrong.

The word also describes things that seem admirable or appealing in a way that's hard to define exactly. A new skateboard trick might be cool, or a clever solution to a math problem, or the way someone stands up for a friend. What seems cool changes over time and from person to person. Your grandparents might have thought bell-bottom jeans were cool, while you might think they look ridiculous.