decamillennium means A period of time consisting of ten thousand years. Lexicurio rates it Rare gem — a strength score of 82 out of 100.
Etymology
From deca- + millennium.
noun
- A period of time consisting of ten thousand years.“A Millennium consists of one thousand years. / A Decamillennium is ten thousand years. / […] / A Centimillennium embraces a period of one hundred thousand years.”