1. To spread or unfold outward. As we came out of the mountain pass, the road opened up and the great plains lay before us.

2. Of an establishment, to begin operation for the first time. I hear there's a new movie theater opening up across town.

3. To open at the beginning of the business or work day. What time in the morning do you typically open up? My office building opens up at 7 AM, so I'll be able to get in early and make some tweaks before the meeting.

4. To fire or begin firing a gun (at someone). The troops opened up as soon as they saw the militants exit the building.

5. By extension (of meaning 4), to begin attacking, criticizing, or interrogating someone. The reporters opened up on the commissioner with a barrage of intense questions.

6. To speak candidly; to reveal one's inner thoughts or emotions. Often followed by "with/to (someone)." I've been trying to get Jeff to open up a bit, but he just likes to keep things to himself. You need to learn to open up to your wife, or your relationship is doomed for failure.

7. To become available or viable. The company is so massive that there are jobs opening up all the time. With recent changes in the legislation, that region is opening up as a potential new market.