Isthmus \Isth"mus\ (?; 277), n.; pl. Isthmuses. [L. isthmus, Gr. 'isqmo`s a neck, a neck of land between two seas, an isthmus, especially the Isthmus of Corinth; prob. from the root of 'ie`nai to go; cf. Icel. ei[eth] isthmus. See Issue.]

(Geog.) 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.

Isthmus of the fauces. (Anat.) See Fauces.

Source: Webster's Revised Unabridged Dictionary (1913)