Card tart means: British informal term for a 'rate tart' -- someone who habitually moves their credit card balance between providers to exploit introductory 0% interest offers before the rate rises. The behavior is. 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.