Petotetremar

Petotetremar is equal to \(f_{\psi(M\uparrow\uparrow 10^{15})}(10)\). The term was coined by Denis Maksudov

Etymology
The 3 parts of the name, "peto", "tetr" and "emar", mean \(1\ \text{quadrillion}\), the "in-" operation. So the full name indicates the ordinal index of the number.