1. The act of giving up something of value for the sake of something else. For example, you might sacrifice your free time to study for an exam.
2. The act of killing someone or something as an offering to a god or gods. This practice was common in many ancient religions, and is still practiced today in some cultures.
3. The thing that is given up or killed in a sacrifice. For example, the ancient Greeks would often sacrifice animals to their gods.
In a more general sense, sacrifice can refer to any act of giving up something of value for the sake of something else that is considered to be more important. For example, you might sacrifice your personal comfort in order to help someone in need.