Thanks for chiming in everyone! It's been helpful. Everyone seems to agree that it's something like the the "process and intention" that @smceccarelli mentioned. Part of the reason I asked this question is that, I recently spent a TON of time on a single painting and I was really just kind of meh about its outcome. It's alright, but I like a lot of my sketches better... so it led to this question.
@Braden-Hallett Wikipedia! I didn't even think of looking there. Good call
@nadyart I really love that raw quality as well, whether they are sketches or finished pieces, and I guess, it's hard for me to tell sometimes if something that is "raw" is unfinished or not. Maybe the question should be more, something like, refined vs. "sketchy" in a final piece of art, and where does one draw the line (excuse the pun) between something that is supposed to be raw and something that is just not finished?
@neschof I hear what you're saying about people on instagram... I see this amazing painting and they call it a sketch and I'm like, man, I can't do that if I spend a month working on a single piece. Sigh.
@KaraDaniel I really like loose figure drawings as well! I've spent a lot of time painstakingly finishing drawings, and I've learned a lot, but I almost never like the refined, fully rendered pieces as much as faster, looser, more expressive pieces.
@A-G-Meade I like what you're saying about the "intent" to flesh it out later, or use it in a more considered way. There's that word intent again.
@Heather-Boyd I hear what you're saying about process here. It's almost as if the definition of a sketch is really up to the artist. A sketch is not really something that the outside world can determine, but a part of your own process, so it doesn't matter that someone's sketch looks like someone else's finished painting. I suppose there are those who might think that, say, Sarolla's paintings look like sketches compared to someone really rendered like Ingres, or David, but I don't think anyone would argue that Sarolla was just sketching!
@Phil-Cullen @smceccarelli I think that chasing after keeping the liveliness in the final piece is something that is inherent to artmaking. It seems to me we'll always be chasing it! Thanks for reminding me of that.
Thanks everyone for your responses, it's given me some things to chew on!