Chapter 11: The Firebolt

Simplified Chinese (Mandarin: China)
火弩箭 Huǒ nǔjiàn	火 huǒ = 'fire'. 弩箭 nǔjiàn = 'crossbow arrow'.	Fire Crossbow-arrow
Traditional Chinese (Mandarin: Taiwan)
火閃電 Huǒ shǎndiàn	火 huǒ = 'fire'. 閃電 shǎndiàn = 'lightning'.	Fire Lightning
Japanese
炎の雷（ファイアボルト） Honō no ikazuchi / Faiaboruto	炎 honō = 'flames, fire'. の no = connecting particle 雷 ikazuchi = 'thunderbolt'. ファイアボルト Faiaboruto = 'Firebolt' (English).	Flame thunderbolt / Firebolt
Korean
파이어볼트 Paieobolteu	파이어볼트 paieobolteu 'Firebolt (English)	Firebolt
Vietnamese (Chinese characters show etymology)
Tia chớp	tia chớp = 'lightning bolt'.	Lightning Bolt
Mongolian (new)
Аянга Ayanga	аянга ayanga = 'thunder / lightning'.	Lightning

The 'Firebolt' is Harry's new broomstick.

'Firebolt'

Most of the translations interpret 'bolt' as referring to lightning, that is, a bolt of lightning.

The Chinese-language translation from Taiwan (Traditional characters) uses 火閃電 huǒ shǎndiàn, literally 'fire lightning'.
Japanese uses fine-sounding poetic words for both 'fire' and 'lightning': 炎の雷 honō no ikazuchi. Furigana above the two words indicate that they should be read as faiaboruto 'firebolt'. This gives the meaning of the name in Japanese as well as an approximation of the English pronunciation. (See above, Chapter 3, for furigana).
The Vietnamese (tia chớp) translates only the word 'bolt of lightning', ignoring the 'fire' part.
The Mongolian translation similarly uses only аянга ayanga meaning 'thunder' and 'lightning' together, omitting the word for 'fire'.
The Mainland Chinese version departs completely from the 'lightning bolt' simile to compare the broom to an arrow (or 'bolt') that has been shot from a crossbow.
The Korean translation transliterates English 'Firebolt' into 파이어볼트 paieobolteu. As usual, 'f' is rendered as 'p', and the 'r' in 'fire' is rendered as a vowel (어 eo.)

An advertisement for the Firebolt appears at Chapter 4. The text of the advertisement can be found at The Firebolt in the Passages section.

(Korean appears thanks to "Hiro".)

(Detailed notes on the chapter can be found at Harry Potter Lexicon)