The Collaborative International Dictionary of English v.0.48:

Pardonable \Par"don*a*ble\, a. [Cf. F. pardonnable.]
   Admitting of pardon; not requiring the excution of penalty;
   venial; excusable; -- applied to the offense or to the
   offender; as, a pardonable fault, or culprit.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pardonable
    adj 1: admitting of being pardoned [ant: unpardonable]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "pardonable":
   admissible, allowable, condonable, defensible, dispensable,
   excusable, exemptible, expiable, forgivable, inoffensive,
   justifiable, legitimate, reasonable, remissible, unobjectionable,
   venial, vindicable, warrantable