(arithmetic) The arithmetic operator consisting of repeated exponentiation, by analogy with exponentiation being repeated multiplication and multiplication being repeated addition, ba denoting a to the power of a to the power of ... to the power of a, in which a appears b times. Notation: ba, or
tetra- + (itera)tion; coined by Reuben Goodstein
English Wiktionary. Available under CC-BY-SA license.