The Collaborative International Dictionary of English v.0.48:

Kilometer \Kil"o*me`ter\, Kilometre \Kil"o*me`tre\, n. [F.
   kilometre. See Kilogram, and Meter.]
   A measure of length, being a thousand meters. It is equal to
   3,280.84 feet, or 0.62137119 of a mile.
   [1913 Webster]

WordNet (r) 3.0 (2006):

kilometer
    n 1: a metric unit of length equal to 1000 meters (or 0.621371
         miles) [syn: kilometer, kilometre, km, klick]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "kilometer":
   A, G, M, a, angstrom unit, astronomical unit, block, centimeter,
   chain, chiliad, chiliagon, chiliahedron, chiliarch, chiliarchia,
   cubit, decameter, decimeter, dekameter, ell, em, en, fathom,
   finger, foot, footstep, fur, furlong, grand, hand, inch, kilo,
   kilocycle, kilogram, kilohertz, kiloliter, lakh, league,
   light-year, line, link, meter, micron, mil, mile, millennium,
   millepede, milligram, milliliter, myriad, myriameter, nail,
   one hundred thousand, pace, palm, parsec, perch, pica, point, pole,
   rod, step, stride, ten thousand, thou, thousand, wavelength,
   yard