(1) The opposite of real-time, i.e., processing to an audio or other file which is not done at the same time as the human actions which initiate the processing.
(2) In the videotape editing process, off-line is when the final edit list is compiled (on a less expensive machine), i.e., where only the EDL is created, but not conformed, in preparation for the final edit. On-line is where the video tape master is created from the EDL, including all effects using high-quality equipment, usually a 1″ video deck.
(3) In a network, any device which is able/unable to receive or transmit a signal.
(4) In a system of synchronized devices, a slave device which is waiting for a particular time code value to be reached before it will play or record, etc., is said to be on-line.