Noun
A neck or narrow slip of land by which two continents are connected, or by which a peninsula is united to the mainland; as, the Isthmus of Panama; the Isthmus of Suez, etc.
Source: Webster's dictionaryThis narrow isthmus 'twixt two boundless seas, The past, the future,two eternities. Thomas Moore
I desire to have both heaven and hell ever in my eye, while I stand on this isthmus of life, between two boundless oceans. John Wesley
There are continents and seas in the moral world, to which every man is an isthmus or inlet, yet unexplored by him. Henry David Thoreau
The Central American isthmus is a region of great contrasts, but also of heartening unison. Millions of men and women share dreams of freedom and progress. Oscar Arias Sanchez
If, presume not to God to scan; The proper study of Mankind is Man. Plac'd on this isthmus of a middle state, A being darkly wise, and rudely great. Alexander Pope
Archaeology has shown that some Roman forts south of the Forth–Clyde isthmus were rebuilt and enlarged, although others appear to have been abandoned. Source: Internet