SG Heritage Dictionary

Millionth [Adjective] Webster's Dictionary 1828

The ten hundred thousandth.

Millionth [Adjective] Webster's Dictionary 1913

Being the last one of a million of units or objects counted in regular order from the first of a series or succession; being one of a million.

Millionth [Noun] Webster's Dictionary 1913

The quotient of a unit divided by one million; one of a million equal parts.