from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A unit of mass equal to one thousandth (10-3) of a milligram or one millionth (10-6) of a gram.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A unit of mass equal to 0.000 001 grams. Symbol: μg or mcg
from The Century Dictionary and Cyclopedia
- n. The millionth part of a gram, being about of a grain troy.
- n. A photograph or a drawing of a microscopic object.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. one millionth (1/1,000,000) gram
micro- + gram (Wiktionary)