impregnable

adjective

1. strong enough to resist or withstand attack; not to be taken by force, unconquerable: an impregnable fort.
2. not to be overcome or overthrown: an impregnable argument.

adjective

1. susceptible to impregnation, as an egg.

adjective

1. unable to be broken into or taken by forcean impregnable castle
2. unable to be shaken or overcomeimpregnable self-confidence
3. incapable of being refutedan impregnable argument

adjective

1. able to be impregnated; fertile

adj.

early 15c., imprenable “impossible to capture,” from Middle French imprenable “invulnerable,” from assimilated form of in- “not, opposite of” (see in- (1)) + Old French prenable “assailable, vulnerable” (see pregnable). With intrusive -g- 16c., on model of deign, reign, etc. Related: Impregnability.