geographical definition of isthmus
1. a narrow strip of land, bordered on both sides by water, connecting two larger bodies of land. 2. a relatively narrow passage or strip of tissue joining two cavities or parts of an organ.isthmos isthmÃ³s narrow, passage]. isthmusâ²isth, moid. adj. (Physical Geography) a narrow strip of land connecting two relatively large land areas. 2. (Anatomy) anatomy. a. a narrow band of tissue connecting two larger parts of a structure. b. a narrow passage connecting two cavities. [C16: from Latin, from Greek isthmos ]. (ËÉªs mÉs). n., pl. -musâ¢es, -mi (-mÄ«).