1. a unit of length equal to one thousandth of a micron or one billionth of a meter
Usage: scientific; largely obsolete

Examples

• The wavelength of blue light is approximately 450 millimicrons.
• Scientists measured particles in the range of 100 to 500 millimicrons.
• The term millimicron has been largely replaced by nanometer in modern usage.
• Virus particles typically measure between 20 and 300 millimicrons in diameter.
• The resolution of the microscope was limited to structures larger than 200 millimicrons.
• Researchers found that the protein molecules were about 5 millimicrons in length.