The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster]WordNet (r) 3.0 (2006):
millimeter n 1: a metric unit of length equal to one thousandth of a meter [syn: millimeter, millimetre, mm]