1. stay up - Verb
2. stay up - Phrase
not go to bed
Source: WordNetCockroaches and socialites are the only things that can stay up all night and eat anything. Herb Caen
Never stay up on the barren heights of cleverness, but come down into the green valleys of silliness. Ludwig Wittgenstein
Never go to bed angry, stay up and fight. William Congreve
I tend to stay up late, not because I'm partying but because it's the only time of the day when I'm alone and don't have to be performing. Jim Carrey
An empty bag will not stay up. Mexican Proverb
Had you gotten up early, you wouldn't have needed to stay up late. Yiddish Proverb