from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An extremely small bubble, usually only a few hundred micrometers in diameter, that can be uniformly suspended in a liquid such as blood.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A microscale bubble, used in medical diagnostics as a contrast agent for ultrasound imaging.
micro- + bubble (Wiktionary)