We don't have synonyms for rastra yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are rasta, astra and castra.
(n) :
Alternative form of arrastra. [A device formerly used by gold-miners for grinding auriferous quartz, crudely resembling a mortar and pestle, with the crushing element dragged around by horse or mule.]
(n) :
Alternative form of arrastra. [A device formerly used by gold-miners for grinding auriferous quartz, crudely resembling a mortar and pestle, with the crushing element dragged around by horse or mule.]