The Collaborative International Dictionary of English v.0.48:

Quartern \Quar"tern\, n. [OE. quarteroun, quartron, F.
   quarteron, the fourth part of a pound, or of a hundred; cf.
   L. quartarius a fourth part, quarter of any measure,
   quartern, gill. See Quarter, and cf. Quarteron,
   Quadroon.]
   1. A quarter. Specifically:
      (a) The fourth part of a pint; a gill.
      (b) The fourth part of a peck, or of a stone (14 ibs.).
          [1913 Webster]

   2. A loaf of bread weighing about four pounds; -- called also
      quartern loaf. --Simmonds.
      [1913 Webster]

WordNet (r) 3.0 (2006):

quartern
    n 1: one of four equal parts; "a quarter of a pound" [syn: one-
         fourth, fourth, one-quarter, quarter, fourth part,
         twenty-five percent, quartern]