old-line

From old +‎ line (“stated positions of a political or religious group”). Attested from the 19th century, originally in the United States.

old-line (comparative more old-line, superlative most old-line)

1. Reactionary or conservative.
   • 1856, James B. Clay, “Speech of James B. Clay Delivered at the Union Meeting in Mason County, Kentucky”, in Old Line Whigs for Buchanan & Breckinridge‎, page 15:

     I am deliberately convinced that Mr. Filmore has not the least chance of success, and that if it be at all possible to defeat Fremont, the Democratic party, with their candidates Buchanan and Breckinridge, with the aid of the Union-loving Old-line Whigs, is the only party which has the least chance to do so.

2. Long-established.
   • 1908, T.D. O'Brien, “Mutual Insurance”, in Farm Implements‎, page 37:

     One of the old line insurance companies said to me recently, that they never made anything out of their underwriting business, but made their profit out of the investments of the reserved fund

   • 2000, George Alexander, quoting Chuck James, “Harvesting an e-commerce solution”, in Black Enterprise‎, page 118:

     I also started reading a great deal about Internet transactions and the impact of the Web on more old-line businesses

• “old, adj.”, in OED Online ⁠, Oxford, Oxfordshire: Oxford University Press, March 2004.