Meginemar

Meginemar is equal to \(f_{\psi(\underset{10^6+1\;M\text{'s}}{\underbrace{M_{M_{\cdots_M}}}})}(10)\). The term was coined by Denis Maksudov.

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