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)