The Collaborative International Dictionary of English v.0.48:

Feckless \Feck"less\, a. [Perh. a corruption of effectless.]
   Spiritless; weak; worthless. [Scot]
   [1913 Webster]

WordNet (r) 3.0 (2006):

feckless
    adj 1: not fit to assume responsibility
    2: generally incompetent and ineffectual; "feckless attempts to
       repair the plumbing"; "inept handling of the account" [syn:
       feckless, inept]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "feckless":
   aimless, barren, bootless, carefree, careless, counterproductive,
   easygoing, effete, empty, etiolated, fatuitous, fatuous, fruitless,
   fustian, futile, good-for-nothing, grasshopper, happy-go-lucky,
   heedless, impotent, improvident, inadequate, inadvertent, inane,
   incautious, ineffective, ineffectual, inefficacious, inoperative,
   invalid, irresponsible, lackadaisical, meaningless, negligent,
   no go, nonchalant, nugacious, nugatory, of no force, of no use,
   pointless, purposeless, reckless, remiss, shiftless, sterile,
   superfluous, thoughtless, thriftless, unavailing, uncaring,
   undependable, uneconomical, unheeding, unproviding, unpurposed,
   unreflective, unreliable, unthinking, unthrifty, untrustworthy,
   useless, vain, wild, worthless, wrecking