WordNet (r) 3.0 (2006):

get on
    v 1: have smooth relations; "My boss and I get along very well"
         [syn: get along with, get on with, get on, get
         along]
    2: get on board of (trains, buses, ships, aircraft, etc.) [syn:
       board, get on] [ant: get off]
    3: get up on the back of; "mount a horse" [syn: hop on,
       mount, mount up, get on, jump on, climb on,
       bestride] [ant: get off, hop out]
    4: grow late or (of time) elapse; "It is getting on midnight--
       let's all go to bed!"
    5: appear in a show, on T.V. or radio; "The news won't be on
       tonight" [syn: get on, be on]
    6: develop in a positive way; "He progressed well in school";
       "My plants are coming along"; "Plans are shaping up" [syn:
       progress, come on, come along, advance, get on,
       get along, shape up] [ant: regress, retrograde,
       retrogress]
    7: grow old or older; "She aged gracefully"; "we age every day--
       what a depressing thought!"; "Young men senesce" [syn:
       senesce, age, get on, mature, maturate]

Moby Thesaurus II by Grady Ward, 1.0:

144 Moby Thesaurus words for "get on":
   achieve success, advance, age, arrive, assume, back, be a success,
   be getting along, be so, be such, bestraddle, bestride, board,
   break through, buzz off, change, cheat the undertaker, clear,
   clear the hurdle, climb on, come along, come away, come on,
   come out, come through, contrive, cut a swath, cut the mustard,
   decline, depart, do, do well, dodder, don, draw on, dress in,
   engineer, enjoy prosperity, exit, fade, fail, fare, farewell,
   gang along, get ahead, get along, get away, get by, get in,
   get into, get off, get on swimmingly, get on well, get there,
   get under way, go, go aboard, go along, go away, go far, go off,
   go on, go on board, go on with, go places, go well, grow old,
   hack it, hang in, hang tough, have it made, hop in, jump in,
   keep at it, leave, make a breakthrough, make a success, make good,
   make headway, make it, make out, make progress, make the grade,
   make the scene, manage, manage somehow, march, march off, mosey,
   mount, move, move away, move off, move out, muddle through,
   negotiate, never say die, persevere, persist, pile in, proceed,
   progress, prosper, pull out, put on, put over, put through, rise,
   sashay, sashay off, scrape along, see it through, shake, shape up,
   shrivel, sink, slip on, stack up, stagger, stagger along,
   stick it out, stick to it, succeed, succeed in, survive, swing,
   swing the deal, take flight, take wing, throw, toddle along,
   totter, turn gray, turn out, turn out well, turn white, up and go,
   wane, waste away, wing it, wither, wizen, worry along, wrinkle