0 Old HSK word(s):
火速回电* *

Definitions from Unihan Copyright © 1991-2015 Unicode® Inc. All rights reserved.

火 fire, flame / burn / anger, rage
速 quick, prompt, speedy
回 return, turn around / a time
电 electricity / electric / lightning
Hsk Characters:
HSK -Characters and beyond:
GbBig5EngRadMegaTripleMultilingual