fir·ma·ment / ˈfərməmənt/ • n. poetic/lit. the heavens or the sky, esp. when regarded as a tangible thing. ∎ fig. a sphere or world viewed as a collection of people: one of the great stars in the American golfing firmament.DERIVATIVES: fir·ma·men·tal / ˌfərməˈmentl/ adj.

firmament XIII. — (O)F. — L. firmāmentum, f. firmāre strengthen, f. firmus FIRM1; see -MENT. The L. word, meaning orig. ‘support, foundation’, was adopted in the Vulg., in imitation of LXX Gr. steréōma (f. stereoûn make firm), as the rendering of Heb. rāḳīaʼ vault of the sky, prob. lit. expanse, f. rāḳīaʼ spread out, beat or tread out, (in Syriac) make firm or solid.