Noun
a narrow isthmus between the Gulf of Corinth and the Saronic Gulf; a canal crosses the isthmus so that navigation is possible between the gulfs
Source: WordNetMegara deserted the Spartan-led Peloponnesian League and allied herself with Athens, allowing construction of a double line of walls across the Isthmus of Corinth and protecting Athens from attack from that quarter. Source: Internet
The Allies prepared to defend the Isthmus of Corinth whilst the fleet was withdrawn to nearby Salamis Island. Source: Internet