The Collaborative International Dictionary of English v.0.48:

Hundredweight \Hun"dred*weight`\, n.
   A denomination of weight, containing 100, 112, or 120 pounds
   avoirdupois, according to differing laws or customs. By the
   legal standard of England it is 112 pounds. In most of the
   United States, both in practice and by law, it is 100 pounds
   avoirdupois, the corresponding ton of 2,000 pounds, sometimes
   called the short ton, being the legal ton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cental \Cen"tal\, n. [L. centum a hundred.]
   A weight of one hundred pounds avoirdupois; -- called in many
   parts of the United States a Hundredweight.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hundredweight
    n 1: a unit of weight equal to 100 kilograms [syn:
         hundredweight, metric hundredweight, doppelzentner,
         centner]
    2: a United States unit of weight equivalent to 100 pounds [syn:
       hundredweight, cwt, short hundredweight, centner,
       cental, quintal]
    3: a British unit of weight equivalent to 112 pounds [syn:
       hundredweight, cwt, long hundredweight]