1. being number one quintillion in a sequence

1. one of a quintillion equal parts of something

Examples

• The quintillionth particle in the sample was finally identified.
• She was the quintillionth visitor to the website.
• Each person owns only a quintillionth of the total wealth.
• The measurement was accurate to the quintillionth of a meter.
• A quintillionth of a second is an incredibly brief moment.
• The quintillionth digit of pi has been calculated by supercomputers.