Hardcore/ˈhɑːrdkɔːr/ Definition 1 of 5Pro Tip 1/2Expressing Intensity Use 'hardcore' to express strong commitment or seriousness in informal settings. He's so hardcore about veganism, he grows his own food. Pro Tip 2/2Not Negative 'Hardcore' implies admiration for someone's dedication, rather than criticism. She's a hardcore environmentalist, respected by her community.