Added 10 October 2026 one-thousandth noun Categories: Describing WordsObscure Words noun ! Definition from WordNet 3.1, Princeton University. More about one-thousandth at Wordnik → Where our words come from → One part in a thousand equal parts. Related Words: thousandthhundredthsmillionthhundredth1000thtrillionthinfinitesimalthousandbillionth Back to today's word