What is Look up ?
Look up is (verb) 1. to turn your eyes upwards She looked up and saw clouds in the sky. 2. to try to find some information in a book I’ll look up his address in the telephone book. Look up the word in the dictionary if you don’t know what it means. 3. to get in touch with Look me up when you’re next in London. 4. to get better Things are looking up.
source: Easier English, Student Dictionary Upper Intermediate Level