MicroDroid = M = microfortnight
3.5-inch floppies, as opposed to 5.25-inch vanilla or mini-floppies and the now-obsolete 8-inch variety. This term may be headed for obsolescence as 5.25-inchers pass out of use, only to be revived if anybody floats a sub-3-inch floppy standard. See stiffy, minifloppies.
--The Jargon File version 4.3.1, ed. ESR, this entry manually entered by rootbeer277.