glad rags

noun[plural only]2

1. •
   (slang) Formal attire, dress clothes.

   • “But say, you wouldn’t have known me if you’d seen me here with my wife that time—my glad rags on, a stove-pipe lid, patent leather kicks and a stone on my front. […] — 1896
2. •
   (slang) Stylish clothing.

   • Lock Jaw said, “Bessie, how would you like to get dressed up in a grand worth of glad rags and go to a fancy blowout with me?” — 1969