Definition of "coinbase"

The transaction that created new Bitcoins would be referred to as the coinbase of each block.

2015, Nathaniel Popper, “Technical Appendix”, in Digital Gold, 1st edition, New York: Harper

The authors randomly sampled 100 coinbases from the last 20,000 blocks of the blockchain that by the time of the experiment had the highest block-height at 247,054.

2016, Ghassan O. Karame, Elli Androulaki, Bitcoin and Blockchain Security, Artech House, page 92

Coinbase transactions have nothing to do with the US company of the same name. Coinbase is the required first transaction of every block and is the only transaction allowed to bring bitcoins into existence.

2019, Jimmy Song, Programming Bitcoin: Learn How to Program Bitcoin from Scratch, O'Reilly Media, page 164