Uncool means not fashionable, not interesting, or socially awkward in a way that makes others think less favorably of you. If someone shows up to a party wearing outdated clothes that everyone stopped wearing years ago, kids might say that's uncool. If a student brags constantly about their grades or tattles on classmates over tiny issues, others might consider that behavior uncool.

The word captures a sense of social awareness: cool people seem to understand unspoken rules about what's acceptable or admirable, while uncool people miss those signals. Being uncool might mean trying too hard to impress others, or not trying at all when effort matters. It could mean being mean-spirited, or awkward, or out of touch with what people your age care about.

What counts as cool or uncool changes constantly and varies between groups. Something uncool in one school might be perfectly normal in another.