white-knuckle (HWYT NUK-uhl) adjective Characterized by extreme nervousness or fear. [From the appearance of blood-drained fists, clenched tightly around something, such as a fairground ride.] -Anu Garg (garg wordsmith.org) "Don't miss its awesome white-knuckle rides including: Shockwave -- Europe's... Sign in to see full entry.