Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sīdĕror, ātus, 1, v. dep. n. [sidus, II. E.], to be blasted or palsied by a constellation, to be planet-struck, to be sunstruck, = sidere afflari, ἀστροβολεῖσθαι: fluviatilium silurus Caniculae exortu sideratur, Plin. 9, 16, 25, § 58: siderati, id. 28, 16, 63, § 226: sideratum jumentum, Veg. 3, 39, 1.