Source : Webster's Revised Unabridged Dictionary (1913)

Unnerve \Un*nerve"\, v. t. [1st pref. un- + nerve.]
   To deprive of nerve, force, or strength; to weaken; to
   enfeeble; as, to unnerve the arm.

         Unequal match'd, . . . The unnerved father falls.
                                                  --Shak.

Source : WordNet®

unnerve
     v : disturb the composure of [syn: {faze}, {enervate}, {unsettle}]