What does ‘OP’ stand for In RootsChat?

[RJ_Paton]

Original Post is what I have always understood that OP is the abbreviation for.

It all depends on the context it can be used to refer either to the Original Post or the Poster, although Post is the more common use here on Rootschat.

[Andy J2022]

At least we are fairly well agreed - and certainly on the first word 

"When I use a word,' Humpty Dumpty said in rather a scornful tone, 'it means just what I choose it to mean — neither more nor less."
- Lewis Carroll 1871 Through the Looking-Glass, and What Alice Found There .