To pay cash to buy something. We were forced to pay cash on the barrelhead for everything at the store.
To make a lot of money at something. The small city cashed in on their success after the winter Olympics.
To exchange something for money. We will cash in the coupons because we need some money.
An action that may fail but has a good chance to succeed. The company took a calculated risk when they opened a new store in a very quiet area.