Buck up

(of a saddle or pack animal) to leap with arched back and come down with head low and forelegs stiff, in order to dislodge a rider or pack.

Informal . to resist or oppose obstinately; object strongly

The mayor bucked at the school board's suggestion.

(of a vehicle, motor, or the like) to operate unevenly; move by jerks and bounces.

to throw or attempt to throw (a rider or pack) by bucking.

to force a way through or proceed against (an obstacle)

The plane bucked a strong headwind.

to strike with the head; butt.

to resist or oppose obstinately; object strongly to.

Football . (of a ball-carrier) to charge into (the opponent's line).

to gamble, play, or take a risk against

He was bucking the odds when he bought that failing business.

to press a reinforcing device against (the force of a rivet) in order to absorb vibration and increase expansion.

an act of bucking. ?

buck for, to strive for a promotion or some other advantage

to buck for a raise.

buck up, to make or become more cheerful, vigorous, etc.

She knew that with a change of scene she would soon buck up.

verb

bring down , depress , dishearten

verb

cheer , encourage , hearten , bolster , boost , lift , buck