The Collaborative International Dictionary of English v.0.48:
Permissible \Per*mis"si*ble\, a. That may be permitted; allowable; admissible. -- Per*mis"si*ble*ness, n. -- Per*mis"si*bly, adv. [1913 Webster]WordNet (r) 3.0 (2006):
permissibly adv 1: in a permissible manner [syn: permissibly, allowably] [ant: impermissibly]