breakneck /ˈbɹeɪkˌnɛk/noun 2adjective 1adverb 1forms 3 noun2 •A fall that breaks the neck. •A dangerous steep place from which one could fall and be injured. adjective1 •Dangerously fast; hell-for-leather.He came running around the corner at a breakneck pace and couldn't stop in time to avoid hitting the fruit stand. adverb1 •Dangerously fast.I ran breakneck another hundred yards. — 2009 formsbreaknecks · more breakneck · most breakneck