v.1. To move close together to form a tight group; cluster: The kids bunched up in a corner of the room, whispering to each other.
2. To pack some people or things together tightly: Bunch up the blankets and stuff them into the bag. I didn't like what I had written on the page, so I bunched it up and threw it out.
3. To come together or be more concentrated in one place: The cloth bunches up at the cuff of my shirt.