"ingross" means: Prior to the abolition of inrollment in 1849, to engross a Parliamentary bill prior to royal assent by preparing it on a roll, incorporating.... 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.