Cartographic connectors

• Necks in the water?
• Land mass connectors (Var.)
• Panama Suez and Corinth
• Is the contracted motorway to provide narrow junctions?
• Narrow land strips
• Narrow land formations
• They're bicoastal
• Panama and others

Wiktionary Word definitions in Wiktionary
n. (plural of isthmus English)

WordNet Word definitions in WordNet
See isthmus