I. -n(t)th adjective
1. : being number one trillion in a countable series — see number table
2. : being one of a trillion equal parts into which anything is divisible
II. noun
( plural trillionths -yən(t)s, -yən(t)ths)
1. : number one trillion in a countable series
2. : the quotient of a unit divided by one trillion : one of a trillion equal parts of anything
3. : a minute part