Abu check means: A verification call among football fans to confirm someone's anti-Manchester United stance is genuine and consistent, not just convenient when United are doing well. Rooted in UK football culture. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. It is sporting vocabulary and harmless in itself. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.