The Collaborative International Dictionary of English v.0.48:

Negligible \Neg"li*gi*ble\, a. [Cf. F. n['e]gligible,
   n['e]gligeable.]
   That may be neglected, disregarded, or left out of
   consideration; too small or unimportant to be worthy of
   notice.
   [1913 Webster]

         Within very negligible limits of error.  --Sir J.
                                                  Herschel.
   [1913 Webster]

WordNet (r) 3.0 (2006):

negligible
    adj 1: so small as to be meaningless; insignificant; "the effect
           was negligible"
    2: not worth considering; "he considered the prize too paltry
       for the lives it must cost"; "piffling efforts"; "a trifling
       matter" [syn: negligible, paltry, trifling]