We don't have synonyms for kuoyu yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are guoyu.
(n) :
Alternative spelling of Guoyu. [The standardized spoken Chinese language, also referred to as Standard Mandarin. The term remains in common use in the Republic of China (Taiwan) and colloquially in Hong Kong (along with Putonghua). In mainland China, Guoyu or Taiwan Guoyu is used to refer to Taiwanese Mandarin (standard), as opposed to mainland standard Mandarin.]
(n) :
Alternative spelling of Guoyu. [The standardized spoken Chinese language, also referred to as Standard Mandarin. The term remains in common use in the Republic of China (Taiwan) and colloquially in Hong Kong (along with Putonghua). In mainland China, Guoyu or Taiwan Guoyu is used to refer to Taiwanese Mandarin (standard), as opposed to mainland standard Mandarin.]