"amber gambler" means: A driver of a road vehicle who accelerates when the traffic lights change from green to amber (instead of stopping, as required by law), gam.... 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.