1. To make available
2. To make plain or visible; disclose
3. To open by cutting into
4. To spread out or come into view
5. To commence firing
6. To become communicative
7. To talk freely and without inhibition.

1. When you open something up, you reveal what is inside so that people can see it.
2. When you open a room or building up, you unlock or open the doors so that people can enter.
3. When a new business starts, it opens up or is opened up by someone.