We don't have synonyms for castus yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are cactus, cantus and cestus.
(N) :
an enslaved Gallic man who, together with the Thracian Spartacus, the fellow Gaul Crixus, and Celt Gannicus, alongside Oenomaus, was one of the leaders of rebellious slaves during the Third Servile War.
(N) :
an enslaved Gallic man who, together with the Thracian Spartacus, the fellow Gaul Crixus, and Celt Gannicus, alongside Oenomaus, was one of the leaders of rebellious slaves during the Third Servile War.