Game jam
Also said as Jam
An event where people make a whole small game in a fixed short time, often 48 hours, usually to a theme. Ludum Dare has run since 2002 and the Global Game Jam since 2009.
A hard limit forces you to find the smallest version of an idea and finish it. Finishing is a skill, and most people practise it far too rarely.
Say it
“Let's jam it this weekend. Two people, 48 hours, one mechanic, and we throw out anything that is not playable by Saturday night.”
Where you’ve seen it
Baba Is You started at Nordic Game Jam in 2017, and Superhot started in the 7 Day FPS jam in 2013. Both ideas were small enough to test in days, and both became full commercial games.
Not to be confused with hackathon
A hackathon usually builds a product demo, often judged by sponsors. A jam is about making and finishing a game, and most have no prize worth the name.