<jargon> 1. Ready for use. E.g. "The graph plotter's fixed
and on-line again".

2. Interactive as opposed to batch. Accessible via a
computer (or terminal), rather than on paper or other
medium.

3. Of a user, actively using a computer system, especially the
Internet. E.g "I haven't been on-line for three days."

"On-line" should be hyphenated because it is compounded from
two words but the hyphen is often omitted in names of
organisations or services.

(1998-12-22)