Source : Webster's Revised Unabridged Dictionary (1913)

Mad \Mad\, a. [Compar. {Madder}; superl. {Maddest}.] [AS. gem?d,
   gem[=a]d, mad; akin to OS. gem?d foolish, OHG. gameit, Icel.
   mei?a to hurt, Goth. gam['a]ids weak, broken. ?.]
   1. Disordered in intellect; crazy; insane.

            I have heard my grandsire say full oft, Extremity of
            griefs would make men mad.            --Shak.

   2. Excited beyond self-control or the restraint of reason;
      inflamed by violent or uncontrollable desire, passion, or
      appetite; as, to be mad with terror, lust, or hatred; mad
      against political reform.

            It is the land of graven images, and they are mad
            upon their idols.                     --Jer. 1. 88.

            And being exceedingly mad against them, I persecuted
            them even unto strange cities.        --Acts xxvi.
                                                  11.

   3. Proceeding from, or indicating, madness; expressing
      distraction; prompted by infatuation, fury, or extreme
      rashness. ``Mad demeanor.'' --Milton.

            Mad wars destroy in one year the works of many years
            of peace.                             --Franklin.

            The mad promise of Cleon was fulfilled. --Jowett
                                                  (Thucyd.).

   4. Extravagant; immoderate. ``Be mad and merry.'' --Shak.
      ``Fetching mad bounds.'' --Shak.

   5. Furious with rage, terror, or disease; -- said of the
      lower animals; as, a mad bull; esp., having hydrophobia;
      rabid; as, a mad dog.

   6. Angry; out of patience; vexed; as, to get mad at a person.
      [Colloq.]

   7. Having impaired polarity; -- applied to a compass needle.
      [Colloq.]

   {Like mad}, like a mad person; in a furious manner; as, to
      run like mad. --L'Estrange.

   {To run mad}.
      (a) To become wild with excitement.
      (b) To run wildly about under the influence of
          hydrophobia; to become affected with hydrophobia.

   {To run mad after}, to pursue under the influence of
      infatuation or immoderate desire. ``The world is running
      mad after farce.'' --Dryden.

Source : WordNet®

like mad
     adv : with great speed or effort or intensity; "drove like crazy";
           "worked like hell to get the job done"; "ran like sin
           for the storm cellar"; "work like thunder"; "fought
           like the devil" [syn: {like hell}, {like crazy}, {like
           sin}, {like thunder}, {like the devil}]