"Blockchains are tamper evident and tamper resistant digital ledgers implemented in a distributed fashion (i.e., without a central repository) and usually without a central authority (i.e., a bank, company, or government)"

Online: Dylan J. Yaga, Peter M. Mell, Nik Roby, Karen Scarfone. Blockchain Technology Overview, October 03, 2018 [NIST Blockchain Technology Overview Draft]