The phrase "southern terminus" refers to the point at the southernmost end or edge of something, such as a road, trail, or geographic area. It indicates the end or starting point in the southern direction. Full definition
All the contestants are seeking to replace US Rep. Chris Gibson (R - Kinderhook), who announced last year that he wouldn't seek re-election to a fourth term in the district, whose southern terminus includes Dutchess and Rockland counties. (nypost.com)
S. Route 202 concurrency; NY 6N for the entire duration within Putnam; NY 9D from NY 301 to the Dutchess County line; NY 52 from its southern terminus to NY 311; NY 164 for its entire duration, and NY 301 for its entire duration. (en.wikipedia.org)
Phase 3 - 6 miles of NC 540 from the southern terminus of Phase 2 at U.S. 64 to NC 55 Bypass near Holly Springs (opened in January 2013) (transportation.gov)