Definitions
1.InterjectionCheer up; take courage; take heart.
2.InterjectionHurry up; make haste.
3.VerbTo become encouraged, reinvigorated, or cheerful; to summon one's courage or spirits; to pluck up courage."I realized I needed to buck up and tackle the problem head-on."
4.VerbTo encourage; to hearten."I knew I had to try and buck up the rest of my team as well."
5.VerbTo do better."You better buck up or you'll never make it."
6.VerbTo dress oneself up smartly; compare (obsolete) buck ("a fop, dandy") .mw-parser-output .defdate{font-size:smaller}
7.VerbTo pass on to higher authority for resolution. See also pass the buck."He started bucking up everything to management when he didn't get a raise.; He just bucked everything risky up to management.; Instead of dealing with the customer's complaint himself, he just bucked it up to his boss."
8.VerbTo hurry up.
9.VerbTo hit or fight (someone).