Of a place of defence or confinement: Strong, stout; formidable, powerful. Obsolete.

Of a fortress, town, country, or military position: difficult to capture or invade; well able to withstand assault; having powerful artificial or…

Of a place: fortified. Cf. fasten, v. 2a. Obsolete.

= impregnable, adj.

Architecture. Furnished with battlements, crenellated.

? Fortified.

Fit for warfare.

Of a fortress or stronghold: That cannot be taken by arms; incapable of being reduced by force; capable of holding out against all attacks.

That cannot be taken by assault or storm; incapable of being overcome, subdued, or overthrown by… literal of a fortress, an army, etc.

Chiefly Scottish. Of a position or structure: able to withstand assault or capture. Obsolete.

Furnished with, protected by, bulwarks.

= inexpugnable, adj.

Strengthened; provided with means of defence; protected with fortifications.

Heavily or fully fortified; esp. provided with good fortifications; made strong or secure.

Not winnable; esp. of fortresses: Impregnable.

Fortified, made strong against attack. Obsolete.

(un-, prefix1 affix 1b.)

Of a fortress, town, etc.: Capable of being defended; strong, well-fortified.

Incapable of being forced or enforced.

Used for impregnable, adj. n.

(un-, prefix1 affix 1b.)

In early use, the strength (of a fortress, defensive work, etc.). Subsequently, the fighting strength (of a ship), as measured by number of guns or…

provided with casemates; (also) strongly fortified.

In extended use, of a building, stronghold, etc.: strongly fortified. Now rare.

Fortified, made strong or secure against attack. Cf. embattled, adj.2

Fairly strong (in various senses).

(un-, prefix1 affix 1b.)