HSK 7-9
火速
huǒsù副
at top speed; at a tremendous lick
急件必须火速送往总部。
Jí jiàn bì xū huǒ sù sòng wǎng zǒng bù.
The urgent document must be sent to headquarters at top speed.
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Appears across levels (7-9) in the HSK 3.0 word list.