Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

mystĭcus, a, um, adj., = μυστικός, of or belonging to secret rites or mysteries, mystic, mystical (poet.): mystica sacra Dindymenes, Mart. 8, 81, 1: vannus Iacchi, Verg. G. 1, 166: vitis, Tib. 3, 6, 1: lampas, Stat. Th. 8, 765.
In plur. subst.: mystĭ-ca, ōrum, n., things pertaining to secret rites, Lampr. Alex. Sev. 26; Inscr. Orell. 2353.
Hence, adv.: mystĭcē, mystically (post-class.), Sol. 32; Ambros. in Luc. 7, § 9.