- a natural junction, running parallel to the E coast of the US, between the hard rocks of the Appalachians and the softer coastal plain, along which rivers form falls and rapids
WordReference Random House Unabridged Dictionary of American English © 2026
fall′ line′,
- Geography, Place Namesan imaginary line, marked by waterfalls and rapids, where rivers descend abruptly from an upland to a lowland.
- Geography, Place Names(caps.) [Eastern U.S.]the imaginary line between the Piedmont and the Atlantic coastal plain.
- Sport[Skiing.]the path of natural descent from one point on a slope to another.
- 1880–85, American.
Collins Concise English Dictionary © HarperCollins Publishers::
Fall Line n