white-knuckle

Short definition from Wiktionary

Adjective

1. 1
   Causing fear, excitement, apprehension, suspense, or nervousness.
2. 2
   Alternative spelling of white-knuckle.

Verb

1. 1
   To endure despite feeling terror, fear, apprehension, anxiety, discomfort, or torment.
2. 2
   To grip tightly in fear, apprehension, suspense, or nervousness.