The Collaborative International Dictionary of English v.0.48:

Rotten \Rot"ten\, a. [Icel. rotinn; akin to Sw. rutten, Dan.
   radden. See Rot.]
   Having rotted; putrid; decayed; as, a rotten apple; rotten
   meat. Hence:
   (a) Offensive to the smell; fetid; disgusting.
       [1913 Webster]

             You common cry of curs! whose breath I hate
             As reek of the rotten fens.          --Shak.
       [1913 Webster]
   (b) Not firm or trusty; unsound; defective; treacherous;
       unsafe; as, a rotten plank, bone, stone. "The deepness of
       the rotten way." --Knolles.
       [1913 Webster]

   Rotten borough. See under Borough.

   Rotten stone (Min.), a soft stone, called also Tripoli
      (from the country from which it was formerly brought),
      used in all sorts of finer grinding and polishing in the
      arts, and for cleaning metallic substances. The name is
      also given to other friable siliceous stones applied to
      like uses.
      [1913 Webster]

   Syn: Putrefied; decayed; carious; defective; unsound;
        corrupt; deceitful; treacherous.
        [1913 Webster] -- Rot"ten*ly, adv. -- Rot"ten*ness,
        n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

rottenly
    adv 1: in a terrible manner; "she sings terribly" [syn:
           terribly, atrociously, awfully, abominably,
           abysmally, rottenly]