Yaar god means: The person in any friend group who is universally, uncontestably the best at being a yaar - the one who shows up, keeps receipts on everyone's dreams, remembers the hard dates, hypes you before. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. 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.