Source : Webster's Revised Unabridged Dictionary (1913)

Millimeter \Mil"li*me`ter\, Millimetre \Mil"li*me`tre\, n. [F.
   millim[`e]tre; milli- milli- + m[`e]tre. See 3d {Meter}.]
   A lineal measure in the metric system, containing the
   thousandth part of a meter; equal to .03937 of an inch. See
   3d {Meter}.

Source : WordNet®

millimetre
     n : a metric unit of length equal to one thousandth of a meter
         [syn: {millimeter}, {mm}]