In my answer here I used the word acronym to describe the term ACL, which is a term formed from the first letters of the words Access Control List and is pronounced ā'si'ɛl. According to Difference between an acronym and abbreviation? this is a correct usage of the term; however, someone edited my answer, changing the description of the term to abbreviation.
I don't see an option to flag edits, and I suspect it's futile to get into a back-and-forth editing war. What should I do about this?
Technically, acronyms are a kind of abbreviation. So the edit isn't incorrect. It does not seem to be warranted, however. I'd just roll it back if it were my post. If the editor comes back and changes it again, maybe discuss it in the chat room, or flag it for a moderator's attention.
Rolling back the edit is your best bet. That's what the functionality's for, after all.
The extra things you can do are to comment your roll back and your answer explaining how ACL is pronounced.
Go ahead. In fact there is a Cleanup badge for a roll-back and 95 people received it so far. You can rollback not only to the last edit, but also to any subsequent edit.
You can also add a comment for the potential editors expressing your preferences.
I think the OP is the first responsible for the well being of a post.
