From The Collaborative International Dictionary of English v.0.48 :
Assailable \As*sail"a*ble\, a. Capable of being assailed. [1913 Webster]From WordNet (r) 3.0 (2006) :
assailable adj 1: not defended or capable of being defended; "an open city"; "open to attack" [syn: assailable, undefendable, undefended, open]