"emu bob" means: A task assigned to a group of people, especially schoolchildren or army recruits, where they move around an area and pick up rubbish from th.... 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.