This word has been used in many contexts. It’s original mathematic, but has been repurposed in several domains.
Generally, it means that a system which appears to be chaotic will eventually return to a previously-known state. So, if we consider one combination of all variables in a system as a “state,” an ergodic system will eventually return to that state at some point.
(…I think. Seriously, it’s complicated.)
I found the word in relation to interactive fiction. An author proposed a new phrase – “ergodic literature” – to refer to fiction that is non-linear and requires effort on the past of the reader to consume.
The adjective I propose for this function is “ergodic,” which implies a situation in which a chain of events (a path, a sequence of actions, etc.) has been produced by the nontrivial efforts of one or more individuals or mechanisms.
Now, that doesn’t totally fit the original, mathematical description, but it implies a system in which any moment is a collection of variable states.