What is Wake up?
Wake up is (verb) 1. to stop someone’s sleep He was woken up by the sound of the dog barking. 2. to stop sleeping She woke up in the middle of the night, thinking she had heard a noise. Come on, wake up! It’s past ten o’clock. He woke up to find water coming through the roof of the tent. 3. to wake up to something to realise something When is he going to wake up to the fact that he is never going to be promoted?
source: Easier English, Student Dictionary Upper Intermediate Level