Definition - What does Hackathon mean?
A hackathon is a gathering where programmers collaboratively code in an extreme manner over a short period of time. Hackathons are at least a few days - or over a weekend - and generally no longer than a week. While working on a particular project, the idea is for each developer to have the ability and freedom to work on whatever he/she wants.A hackathon is also known as a hackfest or hack day.
Techopedia explains Hackathon
The roots of hackathons are with open source projects and especially noted in the context of OpenBSD development. Recently, a number of companies adopted the hackathon concept - a subject of much debate. Some view a hackathon as a way to allow development teams to work on chosen projects. Non-proponents view it as a bastardization of the concept, given that a company owns the work results. Such critics view hackathons cynically, as merely a way for a company to get free developer work during a weekend or holiday.