Meaning of open-line

o•pen-line

Pronunciation: (ō'pun-līn"), [key]
— adj.
  1. (of a radio or TV show) maintaining open telephone lines to permit listeners or viewers to phone a program with comments, questions, requests, etc.; call-in.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.