Exintar

Exintar is equal to \(f_{\underbrace{C(C(\cdots(C(C(\Omega_{999,999,999,999,999,999\text{-intar }} 2,0),0),\cdots ),0)}_{999,999,999,999,999,999\text{-intar C's}}}(999,999,999,999,999,999)\) using the fast-growing hierarchy with fundamental sequences for Taranovsky notation. The term was coined by wiki user Denis Maksudov.

Etymology
The 3 parts of the name, "exo", "in" and "tar", mean \(10^{18}\), "in-" operation and Tar function (from Taranovsky's notation) respectively, which form \(Tar(999,999,999,999,999,999\text{-intar})\) when concatenated backwards. So the full name indicates how the number is constructed.