1. To tidy or rearrange the bedclothes on one's bed after one has slept in it. Would it kill you to make up your bed in the morning? It only takes a couple minutes! I never feel like I've properly started the day until I've made up my bed.

2. To prepare a bed for one to sleep in by fitting, arranging, or tidying the bedclothes on it. Your brother and sister are in the two spare rooms, so I made up your bed up in the living room. Be sure to make up each guest's bed before they arrive.