from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A rotating magnetic amplifier with specialized windings that allow small changes in power input to produce large changes in power output.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A form of electromechanical amplifier in which an AC motor drives a DC generator
Originally a trademark.(American Heritage® Dictionary of the English Language, Fourth Edition)
But others "amplidyne," for example seem to get added to dictionaries even as their usage is plummeting.