Quadruplet

noun

1. One of four offspring born in a single birth.
2. A group or combination of four associated by common properties or behavior.
3. A group of four notes having the time value of three notes of the same kind.
4. Any combination of four objects or parts grouped, united, or acting together: as, a quadruplet of springs, consisting of four elliptic springs coupled together and acting as one spring. Also called quartet.
5. One of four born at a single birth.