The Collaborative International Dictionary of English v.0.48:

Centner \Cent"ner\, n. [Cf. G. centner a hundred-weight, fr. L.
   centenarius of a hundred, fr. centum a hundred.]
   1. (Metal. & Assaying) A weight divisible first into a
      hundred parts, and then into smaller parts.
      [1913 Webster]

   Note: The metallurgists use a weight divided into a hundred
         equal parts, each one pound; the whole they call a
         centner: the pound is divided into thirty-two parts, or
         half ounces; the half ounce into two quarters; and each
         of these into two drams. But the assayers use different
         weights. With them a centner is one dram, to which the
         other parts are proportioned.
         [1913 Webster]

   2. The commercial hundredweight in several of the continental
      countries, varying in different places from 100 to about
      112 pounds.
      [1913 Webster]

WordNet (r) 3.0 (2006):

centner
    n 1: a unit of weight equal to 100 kilograms [syn:
         hundredweight, metric hundredweight, doppelzentner,
         centner]
    2: in some European countries: a unit of weight equivalent to 50
       kilograms
    3: a United States unit of weight equivalent to 100 pounds [syn:
       hundredweight, cwt, short hundredweight, centner,
       cental, quintal]