The Collaborative International Dictionary of English v.0.48:
Expiable \Ex"pi*a*ble\, a. [See Expiate.] Capable of being expiated or atoned for; as, an expiable offense; expiable guilt. --Bp. Hall. [1913 Webster]WordNet (r) 3.0 (2006):
expiable adj 1: capable of being atoned for