To "split" something means to share it equally between people. It's often used in a restaurant setting. Things that people often "split" include:
- split an appetizer (at a restaurant)
- split a dessert
- split the check
You can split something with another person:
Do you want to split this with me?
Or you can split something between a group of people:
We'll just order a few salads and split them between us.