What is "slug line"

n. 1 A line of abbreviated text at the beginning of each scene in a screenplay that describes the location and time of day 2 A queue for "casual carpoolers" (Slugging) commuting in the Washington, D.C. and Northern Virginia metropolitan area

Slug Line was singer-songwriter John Hiatt's third album, released in 1979, after four years without a record deal. It was his first of two albums with MCA Records.