Chuck off means: To evict someone, e.g. from a form of transport, perhaps for unruly behaviour, or because the final destination has been reached.. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. It is sporting vocabulary and harmless in itself. 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.