I. ˈbilyən(t)th, ˈbiy- adjective
Etymology: billion + -th
1. : being number one billion in a countable series — see number table
2. : being one of a billion equal parts into which anything is divisible
II. noun
( plural billionths -yən(t)s, -yən(t)ths)
1. : number one billion in a countable series
2. : the quotient of a unit divided by one billion : one of a billion equal parts of anything