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1. Deprived of courage and strength
   "the steeplejack, exhausted and unnerved, couldn't hold on to his dangerous perch much longer"

1. Disturb the composure of
   "Good, it shouldn't unnerve him at all";
   - faze, enervate, unsettle, rattle [informal]

See also: afraid, 'fraid [non-standard]

Type of: discomfit, discompose, disconcert, untune, upset