We don't have synonyms for drystone yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are keystone, dry stone and dry-stone.
(adj) :
Alternative spelling of dry-stone. [(of a wall, bridge, building, etc.) Constructed by laying carefully selected stones on top of each other, and bedding them down with no mortar.]
(adj) :
Alternative spelling of dry-stone. [(of a wall, bridge, building, etc.) Constructed by laying carefully selected stones on top of each other, and bedding them down with no mortar.]