The Collaborative International Dictionary of English v.0.48:

Cowardly \Cow"ard*ly\, a.
   1. Wanting courage; basely or weakly timid or fearful;
      pusillanimous; spiritless.
      [1913 Webster]

            The cowardly rascals that ran from the battle.
                                                  --Shak.
      [1913 Webster]

   2. Proceeding from fear of danger or other consequences;
      befitting a coward; dastardly; base; as, cowardly
      malignity. --Macaulay.
      [1913 Webster]

            The cowardly rashness of those who dare not look
            danger in the face.                   --Burke.

   Syn: Timid; fearful; timorous; dastardly; pusillanimous;
        recreant; craven; faint-hearted; chicken-hearted;
        white-livered.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cowardly \Cow"ard*ly\, adv.
   In the manner of a coward. --Spenser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cowardly
    adj 1: lacking courage; ignobly timid and faint-hearted;
           "cowardly dogs, ye will not aid me then"- P.B.Shelley
           [syn: cowardly, fearful] [ant: brave, courageous]

Moby Thesaurus II by Grady Ward, 1.0:

117 Moby Thesaurus words for "cowardly":
   abulic, afraid, anemic, asthenic, bashful, bloodless, caitiff,
   chicken, chickenhearted, coward, cowed, craven, dastardly, daunted,
   debilitated, diffident, dismayed, drooping, droopy, dull, effete,
   etiolated, faint, fainthearted, faintish, fearful, fearing,
   fearsome, feeble, feebleminded, flabby, flaccid, floppy, frail,
   frightened, funking, funky, gone, goosy, gutless, henhearted,
   imbecile, impotent, in fear, infirm, intimidated, invertebrate,
   jumpy, languid, languorous, lily-livered, limber, limp, listless,
   lustless, marrowless, milk-livered, milksoppish, milksoppy, mousy,
   namby-pamby, nerveless, nervous, overtimid, overtimorous,
   panic-prone, panicky, pigeonhearted, pithless, pliable, poltroon,
   poltroonish, pooped, powerless, pusillanimous, rabbity, recreant,
   rubbery, sapless, scared, scary, shaky, shivery, shrinking, shy,
   sinewless, sissified, sissy, skittery, skittish, slack, soft,
   spineless, spunkless, startlish, strengthless, timid, timorous,
   trembling, tremulous, trepidant, trigger-happy, unhardened,
   unmanly, unmanned, unnerved, unstrung, vile, weak, weak-kneed,
   weak-minded, weak-willed, weakhearted, weakly, white-livered,
   worthless, yellow