on-line \¦ ̷ ̷ ¦ ̷ ̷ \adjective (or adverb) 1.: connected to, served by, or available through a system and especially a computer or telecommunications system < an on-line database > especially : on, connected to, or via the Internet < on-line consumers > < went on-line > 2.: done while connected to a computer system < on-line analysis >