dress up phrasal verb ( see also ↑ dress )
1 . to wear special clothes for fun, or to put special clothes on someone
dress up as
He went to the party dressed up as a Chicago gangster.
dress up in
I keep a box of old clothes for the children to dress up in.
dress somebody ↔ up
We dressed him up as a gorilla.
2 . to wear clothes that are more formal than the ones you would usually wear:
It’s a small informal party – you don’t have to dress up.
3 . dress something ↔ up to make something more interesting or attractive:
It was the old offer dressed up as something new.