buck up

Short definition from Wiktionary

Interjection

1. 1
   Cheer up; take courage; take heart.
2. 2
   Hurry up; make haste.

Verb

1. 1
   To become encouraged, reinvigorated, or cheerful; to summon one's courage or spirits; to pluck up courage.
2. 2
   To encourage; to hearten.
3. 3
   To do better.
4. 4
   To dress oneself up smartly; compare (obsolete) buck ("a fop, dandy")
5. 5
   To pass on to higher authority for resolution. See also pass the buck.
6. 6
   To hurry up.
7. 7
   To hit or fight (someone).