breakneck Synonyms

extremely fast unchancy swifter swift subitaneous speedy snappy rushing reckless rash rapid quick precipitous precipitate vertiginous whirlwind winged gone off half-cocked very fast supersonic sonic slap bang high-speed nippy hotheaded spiralling high-risk zippy alacritous daredevil precipitant nimble express expeditious excessive dizzying dizzy darting dangerous careless brisk breathless blistering allegro accelerated FAST fleet flying minacious lively