breakneck

adj

1. Dangerously fast; hell-for-leather.

   “breakneck pace”

   “He came running around the corner at a breakneck pace and couldn't stop in time to avoid hitting the fruit stand.”

   “The line to Dunières conists of a series of breakneck descents almost invariably ended by a violent curve and followed immediately by a panting climb, on which the engine barked thunderously but failed unhappily to maintain its booked speed of 13 m.p.h.”

   “The use of machine learning in this field is hardly new, but the breakneck pace at which it is improving is worrying, Lund says: “With the advent of ChatGPT, the future is bleak.””

adv

1. (not-comparable)Dangerously fast.

   “I ran breakneck another hundred yards.”

noun

1. A fall that breaks the neck.
2. A dangerous steep place from which one could fall and be injured.