buck up(v.+adv.)
1.赶快,加快 hurry up
▲buck up
If you don't buck up we'll be late.如果你不快些,我们就会迟到了。
2.振作起来,打起精神 be more cheerful
▲buck up
Buck up!Lots of people fail their driving test first time.别灰心,许多人首次参加驾驶考试都没通过。
3.加把劲try harder 
▲buck sth ⇔ up
You'd better buck up your ideas if you want to pass the exam.如果你想通过考试,就得加把劲。

用作不及物动词
▲S+～(+A)
When he tried to ride the horse, it bucked wildly.当他试图骑上这匹马时,它突然狂暴地跃了起来。
用作及物动词
▲S+～+n./pron.
It's no use trying to buck the system.企图反抗这种制度是徒劳的。

They are hunting for bucks.他们正在猎雄兔。
He is more interested in making a mark than in making a buck.他对出名比赚钱更感兴趣。