NoDictionaries   Text notes for  
... otium bello furiosa Thrace, otium Medi pharetra...

If the form given, "Thrax, Thracis" is correct, "Thrace" must be ablative; ablative, at least to me, provides no English translation; but based on the Sapphic meter, whose last four syllables are "long, short, long, short," "furiosa" its modifier has a short "a," so Thrace must be nominative." A search into Lewis & Short reveals the form, Thrācē, ēs, citing among others, "Hor. C. 2, 16, 5; 3, 25, 11; and, Latinized, Thrāca, ae, Verg. A. 12, 335; Hor. Ep. 1, 3, 3; 1, 16, 13." Assuming it's nominative, the meaning is "the Thracian fierce in war" or "crazed by war." One must interpolate the verb "rogat" from the prior phrase to complete the meaning: "the Thracian...asks for/seeks peace."