The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

   Panic grass (Bot.), any grass of the genus Panicum.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Panic \Pan"ic\, a. [Gr. paniko`s of or pertaining to Pa`n 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.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Panic \Pan"ic\, n. [Gr. to~ paniko`n (with or without dei^ma
   fear): cf. F. panique. 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.
      [1913 Webster]

   2. By extension: A sudden widespread fright or apprehension
      concerning financial affairs.
      [1913 Webster]

WordNet (r) 3.0 (2006):

panic
    n 1: an overwhelming feeling of fear and anxiety [syn: panic,
         terror, affright]
    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: panic, scare]
    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"

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "panic":
   abject fear, affright, agitation, alarm, anxiety, apprehension,
   apprehensiveness, attack of nerves, awe, bear panic, belly laugh,
   blue funk, blue story, boggle, buck fever, case of nerves,
   cold feet, confound, consternation, cowardice, dirty joke,
   dirty story, discomfit, dismay, double entendre, dread,
   ethnic joke, excessive irritability, fear, fidgetiness, fidgets,
   fight shy, frenzy, fright, frighten, fun, funk, funny story, gag,
   go to pieces, good one, good story, horrification, horror, howl,
   howler, hysteria, jape, jest, jestbook, jib, joke, jump,
   jump a mile, laugh, morbid excitability, nerves, nervosity,
   nervous stomach, nervousness, panic fear, panickiness, phobia,
   play, point, put in fear, put to flight, put to rout, rib tickler,
   riot, rout, scare, scatter, scream, send scuttling, shy, sick joke,
   sidesplitter, sight gag, skedaddle, spell of nerves, sport,
   stage fright, stampede, start, start aside, startle,
   state of nerves, story, terrify, terror, tic, trepidation,
   twitching, uneasiness, unholy dread, unnerve, vellication,
   visual joke, wheeze, wow, yarn



The Free On-line Dictionary of Computing (30 December 2018):

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)