From the second edition (1989):
(ˈsaɪmə) Also 6 syma, 6–9 sima, 7–8 scima, 8–9 cima. [mod.L., a. Gr. κῦµα anything swollen, a billow, a wave, a waved or ogee moulding, the young sprout of a cabbage (in which sense also L. cȳma, whence the botanical use).]
1. Arch. A moulding of the cornice, the outline of which consists of a concave and a convex line; an ogee.
cyma recta: a moulding concave in its upper part, and convex in its lower part. cyma reversa (rarely cyma inversa): a moulding convex in its upper part, and concave in its lower part.
1563 Shute Archit. Cib, 4 partes geue also to Sima reuersa. Ibid. Ciijb, That second parte which remayneth of the Modulus ye shall geue vnto Syma. 1703 Moxon Mech. Exerc. 267 Scima reversa‥Scima recta, or Ogee. 1726 Leoni Alberti's Archit. II. 34b, A Cima inversa of the breadth of two minutes. 1761 Brit. Mag. II. 642 The true cima, or cimaise. 1850 J. Leitch Müller's Anc. Art §249. 258 A base of several plinths and cymas.
2. Bot. = cyme 1 and 2.
1706 Phillips (ed. Kersey), Cyma‥the young Sprout of Coleworts, or other Herbs; a little Shoot, or Branch: But it is more especially taken by Herbalists for the top of any Plant. 1775 Lightfoot Flora Scotica (1792) I. 236 The cyma, or little umbel which terminates the branches.