ultima Thule

[uhl-tuh-muh thoo-lee; Latin oo l-ti-mah too-le] /ˈʌl tə mə ˈθu li; Latin ˈʊl tɪˌmɑ ˈtu lɛ/
noun
1.
(italics) Latin. the highest degree attainable.
2.
the farthest point; the limit of any journey.
3.
the point believed by the ancients to be farthest north.
Also called Thule.
Origin
1655-65; literally, farthest Thule
British Dictionary definitions for ultima Thule

ultima Thule

/ˈθjuːlɪ/
noun
1.
another name for Thule
2.
any distant or unknown region
3.
a remote goal or aim
Word Origin
Latin: the most distant Thule