"adult mode" means: Adult mode is the mental state you switch into when life demands that you actually handle your business — filing taxes, having a difficult c.... 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.