1. sit up - Noun
2. sit up - Verb
not go to bed
change to an upright sitting position
a stomach exercise in which a person sits up from a supine position without using the arms for leverage
Source: WordNetsit-up
Don't stay up so late--you have to go to work tomorrow Source: Internet
We sat up all night to watch the election Source: Internet
He sat up in bed Source: Internet
Ahmadu said they lay down for over 30 minutes at different spots even in drainage channels before they asked them to sit up. Source: Internet
Alpha Centauri's graphics are quite good, but they're not going to make anyone sit up and take notice. Source: Internet
Although he never stood again, he was able to sit up and write several times, and his recovery was viewed so positively that a steamer was fitted out as a seagoing hospital to aid with his convalescence. Source: Internet