1. A method of overloading a predefined amount of space in a buffer, which can potentially overwrite and corrupt data in memory. (SP 800-72) (NISTIR).

Source: The Cyber Glossary, National Security Archive, George Washington University, https://nsarchive.gwu.edu/news/cyber-vault/2018-09-19/cyber-glossary

2. A condition at an interface under which more input can be placed into a buffer or data holding area than the capacity allocated, overwriting other information. Attackers exploit such a condition to crash a system or to insert specially crafted code that allows them to gain control of the system. (SP 800-28; CNSSI-4009) (NISTIR)

Source: National Security Archive Cyber Glossary George Washington University https://nsarchive.gwu.edu/news/cyber-vault/2018-09-19/cyber-glossary