Came across this XKCD graphic, trying to describe the Apollo 5 rocket using just the most common 1000 words in English. Which has led to this page, allowing you to try to express an idea with the same limitations.
So I started to wonder about how to explain MQ, and quickly found that “message” is not in the permitted list. It could be made easier if there were a linked thesaurus, but that takes some of the fun away.
I did get as far as “conversation between computers can continue even when one not running”.