ˈisməs, chiefly Brit sometimes ˈistm- noun
( -es )
Etymology: Latin, from Greek isthmos; perhaps akin to Old Norse eith isthmus, Greek ithma step, motion, ienai to go — more at issue
1. : a narrow strip of land running through a body of water and connecting two larger land areas (as two continents or a peninsula and the mainland)
2. : a contracted part or passage connecting two larger structures or cavities: as
a. : an embryonic constriction separating midbrain from hindbrain
b. : the lower portion of the uterine corpus
c. : the fleshy area on the throat of a fish between the gills
d. : a narrow intermediate portion of the pharynx of many nematodes
e. : the constricted connection between the main parts of a desmid