Source : Webster's Revised Unabridged Dictionary (1913)

Passably \Pass"a*bly\, adv.
   Tolerably; moderately.

Source : WordNet®

passably
     adv : to a moderately sufficient extent or degree; "the shoes are
           priced reasonably"; "he is fairly clever with
           computers"; "they lived comfortably within reason"
           [syn: {reasonably}, {moderately}, {within reason}, {somewhat},
            {fairly}, {middling}] [ant: {unreasonably}, {unreasonably}]