... "Microcontent is information published in short form, with its length dictated by the constraint of a single main topic and by the physical and technical limitations of the software and devices that we use to view digital content today. We've discovered in the last few years that navigating the web in meme-sized chunks is the natural idiom of the Internet. So it's time to create a tool that's designed for the job of viewing, managing, and publishing microcontent. This tool is the microcontent client.

For the purposes of this application, we're not talking about microcontent in the strict Jakob Nielsen definition that's now a few years old, which focused on making documents easy to skim. Today, microcontent is being used as a more general term indicating content that conveys one primary idea or concept, is accessible through a single definitive URL or permalink, and is appropriately written and formatted for presentation in email clients, web browsers, or on handheld devices as needed. A day's weather forcast, the arrival and departure times for an airplane flight, an abstract from a long publication, or a single instant message can all be examples of microcontent."

Anil Dash 2002 in his magazine on www.dashes.com

via Ming the Mechanic

i'd prefer to put a little foucault in this definition. see mediatope I on his concept of statements-as-discursive events (in german) and on "semantic clouds" (partly in english).