What is the meaning of the word "buoy up"?

Definitions:

  1. to become more cheerful copy to clipboard verb
    • After eating icecream, I buoyed up. copy to clipboard
  2. to keep afloat copy to clipboard verb
    • I buoyed up my nibling's new business before it took off on its own. copy to clipboard
  3. to make more cheerful copy to clipboard verb
    • I put on a happy song to buoy up the party. copy to clipboard

Synonyms: