To cheer up is to become happier, or to make somebody else happier. Cheer up, try to cheer up, cheer up the room.
It works both ways round, so a person can cheer up and a thing can cheer them up. As a bare instruction it is either kind or infuriating depending on the day.
1phrasecheer upTo become — or make someone — happier.
“Flowers on the table cheer up the whole kitchen.”
cheer up is a phrase.
Practised in Phrasal Verbs