from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A device used for high-altitude sounding, composed of a small, solid-propellant rocket that is launched from a balloon.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A rocket, powered by solid fuel, that is not lit while on the ground but first carried into the upper atmosphere by a gas-filled balloon, then separated from the balloon and automatically ignited to allow it to achieve a higher altitude.
rock(et)1 + (ball)oon.(American Heritage® Dictionary of the English Language, Fourth Edition)
Blend of rocket and balloon (Wiktionary)