quintillion

Short definition from Wiktionary

Numeral

1. 1
   Either of two very large amounts: A billion billion: 1 followed by eighteen zeros, 10¹⁸.
2. 2
   Either of two very large amounts: A million quadrillion: 1 followed by 30 zeros, 10³⁰.
3. 3
   An unspecified very large number.

Noun

1. 1
   Any very large number, exceeding normal description.