"barb core" means: An aesthetic category defined by the visual and cultural identity of Nicki Minaj and her fanbase — think hot pink, hyper-femme maximalism, l.... This is a fairly neutral word with no inherent risk attached. There is no real cause for parental concern; it is descriptive vocabulary rather than something dangerous. If your child uses it, context will usually make the meaning clear. A brief, curious question about where they heard it is generally enough to know whether to follow up.