"call the ball" means: When landing on a US aircraft carrier: to sight the lights from the multi-colored optical landing system that shows a pilot to be on the cor.... 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.