What does the word unnerve mean?

Usage examples for unnerve

  1. They were almost petrified with horror; anxious to make their friend aware of his danger, yet not daring to call out to warn him, lest a sudden perception of the perils of his situation, and of the proximity of his formidable enemy, should unnerve him, and thus deprive him of the slight chance of escape that remained. – Narratives of Shipwrecks of the Royal Navy; between 1793 and 1849 by William O. S. Gilly