perk up

verb

1. To impart strength and confidence to: buck up, cheer (up), encourage, hearten, nerve. See help/harm/harmless.
2. To regain one's health: come around (or round), convalesce, gain, improve, mend, rally, recover, recuperate. See health/sickness.

Restore to good spirits, liveliness, or good appearance, as in You're exhausted, but a cup of tea will perk you up, or The flowers perked up the whole room. [Mid-1600s]

Definition: cheer
Antonyms: depress

The verb has 2 meanings:

Meaning #1: gain or regain energy
  Synonyms: perk, percolate, pick up, gain vigor

Meaning #2: cause to be alert and energetic
  Synonyms: stimulate, arouse, brace, energize, energise