'cheer up' definitions:

Definition of 'cheer up'

From: WordNet
verb
Cause (somebody) to feel happier or more cheerful; "She tried to cheer up the disappointed child when he failed to win the spelling bee" [syn: cheer, cheer up, jolly along, jolly up]
verb
Become cheerful [syn: cheer, cheer up, chirk up] [ant: complain, kick, kvetch, plain, quetch, sound off]