A Quick and Simple Dictionary

tetration

Noun.  (arithmetic) The arithmetic operator consisting of repeated exponentiation, by analogy with exponentiation being repeated multiplication and multiplication being repeated addition, ^''b''''a'' denoting ''a'' to the power of ''a'' to the power of ... to the power of ''a'', in which ''a'' appears ''b'' times. Notation: ^''b''''a'', ''$auparrowuparrow\; b$ ''or'' $a\; ightarrow\; b\; ightarrow\; 2$.