"kookish" means: Acting like a total kook — weird, eccentric, or a little unhinged in a charming or harmless way. Kookish describes someone whose ideas, beha.... 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.