Source : Webster's Revised Unabridged Dictionary (1913)

Midnight \Mid"night`\, n. [AS. midniht.]
   The middle of the night; twelve o'clock at night.

         The iron tongue of midnight hath told twelve. --Shak.

Midnight \Mid"night`\, a.
   Being in, or characteristic of, the middle of the night; as,
   midnight studies; midnight gloom. ``Midnight shout and
   revelry.'' --Milton.

Source : WordNet®

midnight
     n : 12 o'clock at night; the middle of the night; "young
         children should not be allowed to stay up until midnight"