Definition:
Process Miniature is a technique where new development process proposed is experienced by the team by running the entire process in a very short period of time. Alistair Cockburn uses this term as one of his favorite way of conveying the methodology where the participants play-act one or two releases of the process in a very short period of time.
Peter Merel invented a one-hour process miniature “Extreme Hour” where Extreme Programming(XP) is demonstrated using a sample project and involving the audience. Here audience gets one hour to completely develop and test a product using XP principles such as Pair Programming.
Few more examples for Process miniature are ExtremeTeaching, Code Sprint.
Further Reading:
Book: Agile Software Development by Alistair Cockburn
http://wiki.c2.com/?ProcessMiniature
http://wiki.c2.com/?ExtremeHour
http://wiki.c2.com/?ExtremeTeaching
http://wiki.c2.com/?CodeSprint