preg·na·ble 
(prĕgnə-bəl)
(prĕgnə-bəl)adj.
Being such that attack, seizure, or capture is possible; vulnerable or assailable: a pregnable fortress.
[Middle English preignable, pregnabul, from Old French prenable, pregnauble, from prendre, to grasp, from Latin prehendere, prēndere; see ghend- in the Appendix of Indo-European roots.]
preg′na·bili·ty n.