millimicron

noun, plural mil·li·mi·crons, mil·li·mi·cra [mil–uh-mahy-kruh] /ˈmɪl əˌmaɪ krə/.

1. a unit of length equal to one thousandth of a micron; one-billionth of a meter. Symbol: mμ

noun

1. an obsolete name for a nanometre; one millionth of a millimetre

n.

1. A unit of length that is equal to one thousandth (10-3) of a micrometer or one billionth (10-9) of a meter; nanometer.