unprincipled

from WordNet (r) 3.0 (2006)

unprincipled
    adj 1: lacking principles or moral scruples; "freedom from
           coarse unprincipled calumny"- A.E.Stevenson [ant:
           {principled}]
    2: having little or no integrity

from The Collaborative International Dictionary of English v.0.48

Unprincipled \Un*prin"ci*pled\, a. [Pref. un- not + principled.]
   Being without principles; especially, being without right
   moral principles; also, characterized by absence of
   principle. -- {Un*prin"ci*pled*ness}, n.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

49 Moby Thesaurus words for "unprincipled":
      amoral, conscienceless, corrupt, corrupted, criminal, crooked,
      dark, devious, dishonest, dishonorable, dissolute, doubtful,
      dubious, evasive, felonious, fishy, fraudulent, ill-got,
      ill-gotten, immoral, indirect, insidious, licentious, mercenary,
      not kosher, profligate, questionable, reprobate, rotten, shady,
      shameless, shifty, sinister, slippery, stick-at-nothing,
      suspicious, tricky, unconscienced, unconscientious, unconscionable,
      underhand, underhanded, unethical, unsavory, unscrupulous,
      unstraightforward, venal, without remorse, without shame