buck

• male deer; male rabbit; dollar (slang)
move rapidly and with violence; jump vertically legs stiff and back arched ; bet, gamble (slang)
a buck is a us or australian dollar; an informal use.
a buck is also the male of various animals, including the deer and the rabbit.
if a horse bucks, it jumps into the air wildly with all four feet off the ground.
see also bucked.
when someone makes a fast buck, they make a lot of money quickly, usually by doing something dishonest.
if you pass the buck, you refuse to accept responsibility for something, and say that someone else is responsible.
you say the buck stops here to say that it is your responsibility to deal with a problem, rather than people who are junior to you.
if you buck up or if something bucks you up, you become more cheerful.
if you tell someone to buck up, you are telling them to hurry up; an informal expression.