Source : Webster's Revised Unabridged Dictionary (1913)

Mid \Mid\ (m[i^]d), a. [Compar. wanting; superl. {Midmost}.]
   [AS. midd; akin to OS. middi, D. mid (in comp.), OHG. mitti,
   Icel. mi[eth]r, Goth. midjis, L. medius, Gr. me`sos, Skr.
   madhya. [root]271. Cf. {Amid}, {Middle}, {Midst}, {Mean},
   {Mediate}, {Meridian}, {Mizzen}, {Moiety}.]
   1. Denoting the middle part; as, in mid ocean.

            No more the mounting larks, while Daphne sings,
            Shall list'ning in mid air suspend their wings.
                                                  --Pope.

   2. Occupying a middle position; middle; as, the mid finger;
      the mid hour of night.

   3. (Phon.) Made with a somewhat elevated position of some
      certain part of the tongue, in relation to the palate;
      midway between the high and the low; -- said of certain
      vowel sounds; as, [=a] ([=a]le), [e^] ([e^]ll), [=o]
      ([=o]ld). See Guide to Pronunciation, [sect][sect] 10, 11.

   Note: Mid is much used as a prefix, or combining form,
         denoting the middle or middle part of a thing; as,
         mid-air, mid-channel, mid-age, midday, midland, etc.
         Also, specifically, in geometry, to denote a circle
         inscribed in a triangle (a midcircle), or relation to
         such a circle; as, mid-center, midradius.

Mid \Mid\, n.
   Middle. [Obs.]

         About the mid of night come to my tent.  --Shak.

Mid \Mid\, prep.
   See {Amid}.

Source : WordNet®

mid
     adj : used in combination to denote the middle; "midmorning";
           "midsummer"; "in mid-1958"; "a mid-June wedding" [syn:
           {mid(a)}]