Exotar

Exotar is equal to \(f_{\underbrace{C(C(\cdots(C(C(\Omega_{10^{18}}2,0),0),\cdots ),0)}_{10^{18}\text{ C's}}}(10^{18})\) using the fast-growing hierarchy with fundamental sequences for Taranovsky notation. The term was coined by wiki user Denis Maksudov.

Etymology
The 2 parts of the name, "exo" and "tar", mean \(10^{18}\) and Tar function (from Taranovsky's notation) respectively, which form \(Tar(10^{18})\) when concatenated backwards. So the full name indicates how the number is constructed.