perioecus /pɛɹɪˈiːkəs/ noun1 •(no longer used) Someone living on the same latitude as someone else, but on a different or opposite side of the world; one's antithesis.How comes it to pass, that in the same site, in one latitude, to such as are perioeci, there should be such difference of soil, complexion, colour, metal, air, etc. — 1624 formsperioeci