What is the meaning of Quintillion?

Either of two very large amounts:

1. A billion billion: 1 followed by eighteen zeros, 10.

   A billion billion: 1 followed by eighteen zeros, 10.

   A million quadrillion: 1 followed by 30 zeros, 10.

   An unspecified very large number.

   Any very large number, exceeding normal description.

   nonillion (10)

   quintillion (10)

   Source: wiktionary.org