Hi Wild Flower,
I tend to think of publication as a themed collection of articles, or thoughts. That said, when you open an account with Medium, you write in a publication called “Medium”, how cool is that?
You can certainly use Medium as your blog (why not?) — after all, it is your own personal journalling space where you can write what you want to write. Medium publications are very definitely online journals (they are always on, they provide you with a space where you can write time-sensitive and time-ordered organised articles, provide you with RSS, and you can push it to twitter, and facebook and whatever other social media you like, (ask the Buffer guys), I mean the sky’s the limit).
In case you are worried that they will catch you that you already published elsewhere and they will disqualify you from an entry into the contest, just shhh …. keep it private and share the link with your friends and bring them here. Er … even google will not be able to find it, ;-), how about that?
Finally, good luck with your entry. Actually, everyone who writes in Medium is a winner in life, one way or another, but it always helps to wear the offical lapel, as it were, ;-)
And don’t forget to tag elizabeth tobey, she knows all about Medium useristas!