Meanings
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1
noun
a narrow strip of land connecting two larger land areas and bordered by water on both sides
The Panama Canal crosses the isthmus between North and South America.
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2
noun
a narrow band or passage connecting two larger anatomical structures
A thin isthmus of thyroid tissue joins the gland's two lobes.
Thesaurus
Etymology
Borrowed through Latin isthmus from Greek isthmos, 'neck or narrow passage.' The geographic sense compares a constricted strip of land to a neck joining larger bodies; anatomy later applied the same image to narrow tissue connecting larger parts.