Definition from Wiktionary, the free dictionary
eighty-oneth (plural eighty-oneths)
- A fractional part of eighty-one
- If the diameter of the moon were the same as that of the earth, a body weighing one pound on the earth would weigh only one eighty-oneth part of a pound on the moon. —Garrett Serviss, 1907. The moon: a popular treatise, p. 35.