impregnable
Adjective. (Of a fortress, wall, etc., also used figuratively) Too strong to be penetrated.This is an unmodified, but possibly outdated, definition from Wiktionary and used here under the Creative Commons license. Wiktionary is a great resource. If you like it too, please donate to Wikimedia.
This entry was last updated on RefTopia from its source on 3/20/2012.