What does it mean to be a functionally outgoing introvert?
It means you joke and make small talk with strangers and co-workers and genuinely enjoy it--but when you go home you can't wait to curl up on the couch with a book.
It means you are recharged by treating yourself to a nice breakfast alone in a restaurant; you sip your coffee and write, you make small talk with the waiter, you feel so calm and alive.
It makes two days alone in a national park--where I am now, in a complete and total change of gears, doing a "volunteer" stint--into utter heaven--but when you think about your SigFig far away, you feel that sharp edge of sadness and wish he could just be there too. Or your best friend who lives in Australia.
You love doing things by yourself and you love having one or two people you love to do them with, too. Very often you do crave, seek out and enjoy social interaction, (and you know very well how to successfully seek it out and enjoy it, contrary to popular belief about introverts) but in a choice between a noisy bar or a quiet book, book usually wins even when you remember those handful of times you had chosen bar instead and had much fun and met new, interesting people. Doing things by yourself is in general infinitely preferable to doing things with large groups of people you don't know, but doing things with a small group that includes one or two new people can be a wonderful way to make new friends.
People tell you there's no way you're an introvert, you're too social, because they just don't realize that you're happy and and socially functioning because you just spent all day hiking by yourself.
People try to say that being an extrovert is somehow better. I think those people just aren't listening.