Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† spastĭcus, a, um, adj., = σπαστικός, afflicted with the cramp or spasms, spastic, Plin. 20, 22, 89, § 243; 21, 19, 17, § 132; 25, 5, 24, § 60.