Lewis & Short

spīca, ae (vulg. spēca: rustici, ut acceperunt antiquitus, vocant specam, Varr. R. R. 1, 48, 2.
Neutr. collat. form spī-cum, Varr. ap. Non. 225, 30; Cic. Sen. 15, 51, acc. to Non. 225, 29; Cic. poët. N. D. 2, 42, 110.
Masc. collat. form spīcus, Poët. ap. Fest. s. v. spicum, p. 333 Müll.), f. [root spi-, to be sharp; Gr. σπίλος, rock; σπινός, lean].

  1. I. Prop., a point; hence, in partic., of grain, an ear, spike (syn. arista), Varr. R. R. 1, 48; 1, 63, 2; Cic. Fin. 5, 30, 91; 4, 14, 37; Plin. 18, 7, 10, § 56; Cat. 19, 11: Cererem in spicis intercipit, Ov. M. 8, 292; 9, 689: distendet spicis horrea plena Ceres, Tib. 2, 5, 84: spicas hordaceas gerenti, App. M. 7, p. 191.
    Prov.: his qui contentus non est, in litus harenas, In segetem spicas, in mare fundat aquas, Ov. Tr. 5, 6, 44.
  2. II. Transf., of things of a similar shape.
    1. A. A top, tuft, head of other plants, Cato, R. R. 70, 1; Col. 8, 5, 21; Plin. 21, 8, 23, § 47; 22, 25, 79, § 161; Prop. 4 (5), 6, 74; Ov. F. 1, 76.
    2. B. The brightest star in the constellation Virgo, Cic. poët. N. D. 2, 42, 110; German. Arat. 97; Col. 11, 2, 65; Plin. 18, 31, 74, § 311; Manil. 5, 269.
    3. C. Spica testacea, a kind of brick for pavements, laid so as to imitate the setting of the grains in an ear of corn, Vitr. 7, 1 fin.; cf. spicatus, under spico.
    4. D. Spicus crinalis, a hair-pin, Mart. Cap. 9, § 903 (al. spicum crinale, al. crinale spiclum; but in Lucr. 3, 198, the better reading is spiritus acer, v. Lachm. ad h. l.).