Isthmus

In geography, the Isthmus is a narrow strip of land that connects two areas, which acts as a kind of bridge between the two land masses. In medicine, the Isthmus is the area connecting the two lobes of the thyroid.

How Wikipedia stuffed it up

Whilst Wikipedia does have an article on Isthmus the geographical term as well as on Isthmus the medical term, there is no link between the two. Wikipedia also fails to mention that the term isthmus can be used for more than just geography. The medical term is not, as Wikipedia suggests, called the "thyroid isthmus", it is quite simply called the "isthmus", the exact same term as for the land mass. They do, in a sense, refer to the same thing - a narrow strip that connects 2 things - it is just that one is connecting land while the other is connecting lobes of the thyroid.