A web developer who can do client side (CSS, JS, HTML), server side, and knows the essentials of relational databases and SQL. Understands HTTP and the request/response cycle. Systems/DevOps and newer protocols like websockets or WebRTC are nice to have but only a dealbreaker for specialized projects. The idea is that they should be able to jump in and help out with any part of a web app, or implement a feature top to bottom without having to hand it off to someone else at a boundary.
Someone asked the same question a few days ago and got lots of replies:<p><a href="https://news.ycombinator.com/item?id=9032870" rel="nofollow">https://news.ycombinator.com/item?id=9032870</a>
A buzzword, mostly. I suppose you could use it to mean someone who knows about web development from the back end to the front end, and all the bits and pieces in between.