The Chinese characters for gyōza, a kind of pan-fried dumpling, are 餃子. The word gyōza is a borrowing from Chinese, where it is pronounced jiǎozi in Mandarin and normally refers to the boiled rather than pan-fried variety.
The pronunciation of the Japanese loanword is interesting, departing markedly from the way that Chinese characters are normally read in Japanese -- something like kōshi might have been expected. Gyōza is quite clearly a late borrowing that is modelled directly on the Chinese pronunciation. What is more, it appears to have been borrowed from a Chinese dialect that pronounces the Mandarin sound jiao as giao. (This is the same reason for the old rendering of Beijing as Peking or Yangzi Jiang as Yangtze Kiang, where the 'k' is actually pronounced as 'g').
The characters are quite commonly encountered in Japan, as in the following sign.
It is also not uncommon to see gyōza written in katakana, presumably to mark it as a foreign loanword, and at times in hiragana, as in the sign below, which writes the entire expression o-miyage gyōza in hiragana.
A Google search in August 2003 found the following distribution of forms on the Internet: