The term 'Isthmus Land' refers to a landmass that is connected to two larger landmasses by an isthmus, which is a narrow strip of land. The most famous example of this is PANAMA, which is a 6-letter word that can be used to solve the crossword. PANAMA is a country located in Central America, connecting North and South America. It is known for its canal, which was built in the early 20th century and is still in use today.