1. to prevent something from touching 2. to avoid eating something because it's not healthy 3. not to talk on certain subject especially if it is uncomfortable for someone. 4. not to get weight after losing it.
keep off
Examples
1.Children should keep their hands off matches. 2. I try to keep off salty food. 3. Let's keep off this subject, it's annoying. 4. After getting slimmer, Jane kept off her weight for 5 years.