"hardstuck" means: Stuck at a competitive rank you can't climb out of, no matter how many games you play. 'Hardstuck Diamond', 'hardstuck Gold'. Implies the pl.... 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.