from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An instrument carried aloft, chiefly by balloon, to gather and transmit meteorological data.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A miniature radio carried aloft by an unmanned balloon to broadcast the pressure, temperature, and relative humidity of the upper air and to automatically transmit that information to the ground.
radio + French sonde, sounding line (from Old French, from Old English sund(rāp), sounding (line), from sund, sea).(American Heritage® Dictionary of the English Language, Fourth Edition)