micromillimeter

from WordNet (r) 3.0 (2006)

micromillimeter
    n 1: a metric unit of length equal to one billionth of a meter
         [syn: {nanometer}, {nanometre}, {nm}, {millimicron},
         {micromillimeter}, {micromillimetre}]

from The Collaborative International Dictionary of English v.0.48

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]