We don't have synonyms for guyanas yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are guyana, guianas and guyanan.
(n) :
Alternative spelling of Guianas. [A geographic region in South America consisting of Guyana, Suriname and the French overseas department of French Guiana; sometimes also including the Guayana region of eastern Venezuela and the state of Amapá, Brazil.]
(n) :
Alternative spelling of Guianas. [A geographic region in South America consisting of Guyana, Suriname and the French overseas department of French Guiana; sometimes also including the Guayana region of eastern Venezuela and the state of Amapá, Brazil.]