Source : Webster's Revised Unabridged Dictionary (1913)

Panic \Pan"ic\, n. [Gr. ? (with or without ? fear): cf. F.
   panigue. See {Panic}, a.]
   1. A sudden, overpowering fright; esp., a sudden and
      groundless fright; terror inspired by a trifling cause or
      a misapprehension of danger; as, the troops were seized
      with a panic; they fled in a panic.

   2. By extension: A sudden widespread fright or apprehension
      concerning financial affairs.

Panic \Pan"ic\, n. [L. panicum.] (Bot.)
   A plant of the genus {Panicum}; panic grass; also, the edible
   grain of some species of panic grass.

   {Panic grass} (Bot.), any grass of the genus {Panicum}.

Panic \Pan"ic\, a. [Gr. ? of or pertaining to ? Pan, to whom the
   causing of sudden fright was ascribed: cf. F. panique.]
   Extreme or sudden and causeless; unreasonable; -- said of
   fear or fright; as, panic fear, terror, alarm. ``A panic
   fright.'' --Dryden.

Source : WordNet®

panic
     n 1: an overwhelming feeling of fear and anxiety [syn: {terror}]
     2: sudden mass fear and anxiety over anticipated events; "panic
        in the stock market"; "a war scare"; "a bomb scare led
        them to evacuate the building" [syn: {scare}]
     [also: {panicking}, {panicked}]

panic
     v 1: be overcome by a sudden fear; "The students panicked when
          told that final exams were less than a week away"
     2: cause sudden fear in or fill with sudden panic; "The mere
        thought of an isolation cell panicked the prisoners"
     [also: {panicking}, {panicked}]

Source : Free On-Line Dictionary of Computing

panic
     
        1.  What {Unix} does when a critical
        internal consistency checks fails in such a way that Unix
        cannot continue.  The {kernel} attempts to print a short
        message on the {console} and write an image of memory into the
        {swap area} on disk.  This can be analysed later using {adb}.
        The kernel will then either wait in a {tight loop} until the
        machine is rebooted or will initiate an automatic {reboot}.
     
        {Unix manual page}: panic(8).
     
        2. Action taken by software which discovers some fatal problem
        which prevents it from continuing to run.
     
        (1995-03-01)