What standard describes CSMA/CD?

The term CSMA/CD stands for carrier-sense multiple access with collision detection. It is a MAC (Media Access Control) method used in early Ethernet technology for local area networking. Basically, CSMA/CD works on the bus topology.
Ethernet, IEEE 802.3 defines CSMA/CD, and this is because computers on a default Ethernet network share the same channel. Also, CSMA/CD works in the same way computers work with limited collision. IEEE 802.3 is one of the widely used standard protocols for computer networking and general data communications.