1. (adj)on in operation or operational
"left the oven on"; "the switch is in the on position"
2. (adj)on (of events) planned or scheduled
"the picnic is on, rain or shine"; "we have nothing on for Friday night"
3. (adverb)along, on with a forwardmotion "we drove along admiring the view"; "the horse trotted along at a steady pace"; "the circus traveled on to the next city"; "move along"; "march on"