The Collaborative International Dictionary of English v.0.48:

Bootless \Boot"less\, a. [From Boot profit.]
   Unavailing; unprofitable; useless; without advantage or
   success. --Chaucer.
   [1913 Webster]

         I'll follow him no more with bootless prayers. --Shak.
   [1913 Webster] -- Boot"less*ly, adv. -- Boot"less*ness,
   n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bootless
    adj 1: unproductive of success; "a fruitless search"; "futile
           years after her artistic peak"; "a sleeveless errand"; "a
           vain attempt" [syn: bootless, fruitless, futile,
           sleeveless, vain]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "bootless":
   abortive, barren, counterproductive, effete, empty, etiolated,
   failed, failing, fatuitous, fatuous, feckless, fruitless,
   frustrating, futile, gainless, inadequate, inane, ineffective,
   ineffectual, inefficacious, inoperative, invalid, lame, manque,
   miscarried, miscarrying, nonremunerative, nugacious, nugatory,
   of no effect, of no force, otiose, pointless, profitless,
   purposeless, rewardless, sterile, stickit, stillborn, successless,
   unavailable, unavailing, unfortunate, unproductive, unprofitable,
   unremunerative, unrewarding, unsuccessful, useless, vain, wasteful,
   worthless