get on

1.  Also, get upon. Climb on, mount. For example, They say one should get back on a horse as soon as one's fallen off. [Early 1600s]
2.  See get along, def. 1.
3.  See get along, def. 2.
4.  See get along, def. 4. Also see along in years.
5.  get on in the world or company, etc. Prosper or succeed, as in Her inheritance has helped her get on in society, or Dad asked if Bill was getting on in the company. [Early 1800s]
6.  get on with it. Move ahead, pursue one's work. For example, We've spent enough time talking about it; now let's get on with it. [Early 1800s]
7.  get on for. Advance toward an age, amount, time, and so on. For example, It's getting on for noon, so we'd better eat lunch. This usage is often put in the participial form, getting on for. [Mid-1800]
8.  See turn on, def. 3. Also see the subsequent entries beginning with get on.

Definition: be compatible
Antonyms: disagree

v

Definition: mount
Antonyms: dismount, get off

v

Definition: put clothing on
Antonyms: disrobe, unclothe

The verb has 7 meanings:

Meaning #1: have smooth relations
  Synonyms: get along with, get on with, get along

Meaning #2: get on board of (trains, buses, ships, aircraft, etc.)
  Synonym: board
  Antonym: get off (meaning #1)

Meaning #3: get on the back of
  Synonyms: hop on, mount, mount up, jump on, climb on, bestride

Meaning #4: grow late or (of time) elapse

Meaning #5: appear in a show, on T.V., radio, etc.
  Synonym: be on

Meaning #6: develop in a positive way
  Synonyms: progress, come on, come along, advance, get along, shape up

Meaning #7: grow old or older
  Synonyms: age, mature, maturate