What does Tastris mean in Latin?

Tastris, a proper noun, means “a promontory in Cimbria, likely the same as Skagen in modern Denmark”.

What is the genitive of Tastris?

The genitive singular is Tastris. Tastris is feminine, third declension.

In classical Latin, [ˈtas.trɪs]; in ecclesiastical (church) Latin, [ˈtas.tris].

proper noun · femininethird declension

Tastris f sg (genitive Tastris)

Classical[ˈtas.trɪs]Ecclesiastical[ˈtas.tris]

femininesingulara promontory in Cimbria, likely the same as Skagen in modern Denmark
Promunturium Cimbrorum excurrens in maria longe paeninsulam efficit, quae Tastris appellatur.The Cimbrian promontory projects a long way into the sea, forming a peninsula called Tastris.1906, Pliny the Elder, edited by Karl Friedrich Theodor Mayhoff, Naturalis Historia, page 4.39: