Not to be stormed, or taken by assault; incapable of being subdued; able to resist attack; unconquerable; as, an impregnable fortress; impregnable virtue.

able to withstand attack; "an impregnable fortress"; "fortifications that made the frontier inviolable"

impossible to take by storm

A woman whose memory of labor is still vivid.

Capable of being impregnated, as the egg of an animal, or the ovule of a plant.