1. To physically surround, encircle, or approach someone or something. As the opposing troops closed in on us, I knew we would never win the battle. When I'm in a small space for too long, I start to feel as though the walls are closing in on me.

2. To overwhelm or engulf someone, as of emotions. For a long time, I couldn't drive because feelings of fear closed in on me every time I got behind the wheel.

3. To approach very quickly or become imminent, as of a deadline or other requirement. I procrastinated, and now the deadline for my paper is really closing in on me!