In X-Sequence Hyper-Exponential Notation, Mega Teragygas is equal to 100{(X↑↑X)(X↑↑X)(X↑↑X)X}100. The name (which literally means "Great Monstrous Giant", a reference to Sbiis Saibian's comparably massive Super Monster-Giant) was coined by SuperJedi224. Source: [1]