The Collaborative International Dictionary of English v.0.48:

On \On\, adv. [See On, prep.]
   1. Forward, in progression; onward; -- usually with a verb of
      motion; as, move on; go on; the beat goes on. "Time glides
      on." --Macaulay.
      [1913 Webster]

            The path is smooth that leadeth on to danger.
                                                  --Shak.
      [1913 Webster]

   2. Forward, in succession; as, from father to son, from the
      son to the grandson, and so on.
      [1913 Webster]

   3. In continuance; without interruption or ceasing; as, sleep
      on, take your ease; say on; sing on.
      [1913 Webster]

   4. Adhering; not off; as in the phrase, "He is neither on nor
      off," that is, he is not steady, he is irresolute.
      [1913 Webster]

   5. Attached to the body, as clothing or ornament, or for use.
      "I have boots on." --B. Gonson.
      [1913 Webster]

            He put on righteousness as a breastplate. --Is. lix.
                                                  17.
      [1913 Webster]

   6. In progress; proceeding; ongoing; as, a game is on.
      [1913 Webster]

   Note: On is sometimes used as an exclamation, or a command to
         move or proceed, some verb being understood; as, on,
         comrades; that is, go on, move on.
         [1913 Webster]

   On and on, continuously; for a long time together. "Toiling
      on and on and on." --Longfellow.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "on and on":
   ad infinitum, again and again, always, at a stretch, at all times,
   ceaselessly, connectedly, constantly, continually, continuously,
   cumulatively, cyclically, daily, daily and hourly, day after day,
   day and night, endlessly, ever, ever and anon, ever more,
   every day, every hour, every moment, greater and greater,
   growingly, hour after hour, hourly, incessantly, increasingly,
   interminably, monotonously, month after month, more, more and more,
   night and day, on a stretch, on end, perennially, perpetually,
   rapidly, regularly, repetitively, right along, round the clock,
   steadily, sustainedly, together, unbrokenly, unceasingly,
   unintermittently, uninterruptedly, unrelievedly, unvaryingly,
   without a break, without cease, without letup, without stopping,
   year after year