- The definition of white-knuckle is something tense or something that causes fear and apprehension.
When an airplane has to make an emergency landing which caused extreme nervousness for the flight crew and passengers, this is an example of a white-knuckle landing.
white-knuckle definition by Webster's New World
Origin: from the appearance of a hand clenched in fear
white-knuckle definition by American Heritage Dictionary
also white-knuck·ledadjective Slang