from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A unit of length equal to one thousandth (10-3) of a micrometer or one billionth (10-9) of a meter.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A unit of length equal to one thousandth of a micron
from the GNU version of the Collaborative International Dictionary of English
- n. The thousandth part of a micron or the millionth part of a millimeter; -- a unit of length used in measuring light waves, etc.
from The Century Dictionary and Cyclopedia
- n. A unit of length (μμ) equal to 10 Ångström units, .001 microns, or .000001 millimeters: sometimes employed in microscopy or in stating wave-lengths of light.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a metric unit of length equal to one billionth of a meter
Sorry, no etymologies found.
The units commonly used for this measurement are the millimicron which is denoted by the symbol uu, which equals one millioneth of a millimeter; and the Angstrom Unit (A.U.), which is one-tenth millioneth of a millimeter.