Cis-lunar is a term that I have never heard before. And I have been an astronomy nerd for 50 years.
Cis-lunar means not homo-lunar.
In chemistry the prefix cis- is the opposite of trans-. I’m assuming that since a “trans-neptunian object” is one that orbits beyond Neptune then a cis-lunar orbit would be one lower than the moon, which encompasses most satellites. But then why bother with the complication?
It’s an astrogation term, not necessarily astronomical.
I first read it in an otherwise layman’s-term-using book about the Apollo program, sometime in the mid-70s.
I was 8 at the time of Apollo 17.