From Longman Dictionary of Contemporary Englishuncoolun‧cool /ˌʌnˈkuːl◂/ adjective informal not fashionable or acceptable – used especially by young people Have you seen his shorts? They are just so uncool! It was uncool to get on well with teachers.
Examples from the Corpus
uncool• My parents are so uncool!• But his debut on television after 20 years in books has been so successful that nerds may never again be uncool.• It was grossly uncool doing up.• a really uncool place for a holiday• Nowadays it's considered very uncool to wear fur. 