Rock of Gi·bral·tar /·····/ˌ ˈ/ BrE AmE
the Rock of Gibraltar a narrow mountain area on a ↑ peninsula (=piece of land surrounded on three sides by water) in the south of Spain, at the western end of the Mediterranean Sea. The state of ↑ Gibraltar is there. British people sometimes use the phrase ‘like the Rock of Gibraltar’ to talk about something that is so solid and permanent that it will never break or be destroyed.