Megotetremar

Megotetremar is equal to \(f_{\psi(M\uparrow\uparrow10^6)}(10)\). The term was coined by Denis Maksudov.

Etymology
The 3 parts of the name, "mego", "tetr", and "emar", mean \(10^6\), \(\uparrow\uparrow\), and \(M\). So the full name indicates the ordinal index of the number.