We don't have synonyms for gaiwan yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are taiwan, gaian and gaitan.
(n) :
A Chinese lidded cup or bowl, used to steep tea, sometimes including a saucer, developed during the Ming dynasty as an improvement upon the (lidless) chawan.
(n) :
A Chinese lidded cup or bowl, used to steep tea, sometimes including a saucer, developed during the Ming dynasty as an improvement upon the (lidless) chawan.