Brexit means Brexit

Something you say if you are pursuing a hopelessly vague, potentially catastrophic exercise in national self-harm driven by a misconceived ideology or a bone-headed illusion that you somehow still rule the waves — you know, in the way King Cnut did — you have just found out that you won’t be able to rely on ancient residual powers of the Crown, and you want to brush off uncomfortable questions about what on Earth you think you’re playing at.