Lewis & Short

crusta, ae, f. [cf. crudus], the hard surface of a body, the rind, shell, crust, bark, etc.

  1. I. In gen.: luti, Lucr. 6, 626; cf. soli, Dig. 39, 2, 9: panis, Plin. 19, 8, 53, § 168: glandis, id. 15, 28, 34, § 112: piscium, id. 9, 28, 44, § 83: locustarum, id. 9, 30, 50, § 95: ulcerum, the scab, Cels. 5, 9; cf. id. 5, 10: fluminis, a covering or crust of ice, Verg. G. 3, 360 et saep.
  2. II. In partic., t. t. of plastic art, inlaid, chased, or embossed work on walls or vessels, plasterwork, stucco-work, mosaic work: parietis, Plin. 35, 12, 45, § 154; cf. id. 36, 6, 7, § 48: quae (vasa) probarant, eis crustae aut emblemata detrahebantur, Cic. Verr. 2, 4, 23, § 52; Plin. 36, 6, 6, § 47; 36, 6, 7, § 48: capaces Heliadum crustae, Juv. 5, 38; Dig. 34, 2, 32, § 1.
    1. * B. Trop.: non est ista solida et sincera felicitas; crusta est et quidem tenuis, plaster- or outside-work, Sen. Prov. 6, 3; cf. tectorium.