Webster's Revised Unabridged Dictionary · 1913

Seventieth

Seventieth , adjective

[Anglo-Saxon hund-seofontigoea.]

1.
Next in order after the sixty-ninth; as, a man in the seventieth year of his age.
2.
Constituting or being one of seventy equal parts.

Seventieth , noun

1.
One next in order after the sixty-ninth.
2.
The quotient of a unit divided by seventy; one of seventy equal parts or fractions.