I regularly see the abbreviation
OP used in comments and in questions on the meta site. What does it mean?
Should a glossary be included in the FAQ? Or should
OP be included in an existing glossary I do not know of?
OP means Original Poster, in other words, the user that asked the question.
OP is a term commonly used all over the English speaking Internet, in forums, bug reports and social news sharing sites.
I do not think it should be included in the FAQ, as it is a fairly common term. People who are unfamiliar with it can look up this question or search for it on Google. It's listed in Wiktionary and other online dictionaries.
I agree with Flimm that OP doesn't need to be the FAQ. But I do think it should be in the glossary.
And it is in the glossary! It's somewhat confusingly under "Ask Ubuntu/Stack network specific terms" (even though it's not really specific to SE or AU).
The entry for it says:
OP= Original Poster
Also, people should feel free to ask us what that and any other jargon means (as well as to search for or look up the term, as Flimm suggested).