Source : Webster's Revised Unabridged Dictionary (1913)

Permissible \Per*mis"si*ble\, a.
   That may be permitted; allowable; admissible. --
   {Per*mis"si*ble*ness}, n. -- {Per*mis"si*bly}, adv.

Source : WordNet®

permissible
     adj 1: that may be permitted especially as according to rule;
            "permissible behavior in school"; "a permissible tax
            deduction" [ant: {impermissible}]
     2: that may be accepted or conceded; "a kind of speculation
        that was permissible in cosmology but inadmissible in
        medicine"