'Micromillimeter' definitions:

Definition of 'micromillimeter'

From: WordNet
noun
A metric unit of length equal to one billionth of a meter [syn: nanometer, nanometre, nm, millimicron, micromillimeter, micromillimetre]

Definition of 'Micromillimeter'

From: GCIDE
  • Micromillimeter \Mi`cro*mil"li*me`ter\, n. [Micro- + millimeter.] The millionth part of a meter.
  • Note: The millionth part of a meter is now termed a micron, and the word micromillimeter does not conform to the IS use of the prefix micro-. [1913 Webster +PJC]