Solstitium, solstitij, n. g. Virg.The stay of the sunne when hee cannot go either higher or lower: whiche is in winter the eyght Kalends of Ianuarie, and in summer the eyghte Kalends of July. Solstitium brumale. Colum.
Lewis and Short: Latin dictionary
solstĭtĭum, ii, n. [sol-sisto]. I. In gen., the time when the sun seems to stand still, either in Cancer or in Capricorn, the (summer or winter) solstice (so in gen. not till after the Aug. period): solstitium aestivum ... hibernum, Col. 7, 3, 11: aestivum, Plin. 2, 103, 106, 229: brumale, Col. 11, 2, 94: solstitia et aequinoctia, id. 9, 14, 12.—II. In partic., the summer solstice, the longest day of the year (opp. bruma, the prevalent signif. of the word): alter motus solis est ... a brumā ad solstitium. Solstitium quod sol eo die sistere videbatur, Varr. L. L. 6, 8 Müll.; Cato, R. R. 104; Varr. R. R. 1, 28, 2; 1, 1, 46; Cic. N. D. 2, 7, 19; 2, 19, 50; id. Div. 2, 44, 93; Plin. 8, 43, 68, 167; 18, 28, 68, 264 al.—B.Transf., in gen., summer time, the heat of summer (poet. and in post-Aug. prose; cf. bruma, 2.): paenula solstitio, campestre nivalibus auris Hor. Ep. 1, 11, 18; Verg. G. 1, 100; Ov. Tr. 5, 10, 7; Sen. Ben. 1, 12, 3: solstitium pecori defendite, Verg. E. 7, 47.