in·ex·pug·na·ble 
(ĭn′ĭk-spŭgnə-bəl, -spynə-)
(ĭn′ĭk-spŭgnə-bəl, -spynə-)adj.
1. Impossible to overcome or overthrow by force.
2. Impossible to put aside or drive away: inexpugnable dislike.
[Middle English, from Old French, from Latin inexpugnābilis : in-, not; see IN-1 + expugnābilis, capable of being overcome (from expugnāre : ex-, completely; see EX- + pugnāre, to fight; see IMPUGN).]
in′ex·pug·na·bili·ty n.
in′ex·pugna·bly adv.