What is Unconference?
Unconference meaning A meeting, similar to a conference, but with no agenda fixed in advance. Using various established techniques, participants jointly agree on the day what sessions will run. Some more traditional conference sessions with invited speakers may also be included. A popular format among the tech community, an unconference can be combined with or run alongside a hackathon based on open data. It is a possible method of community engagement by data publishers.
reference: Open Data Handbook – Glossary