Source : Webster's Revised Unabridged Dictionary (1913)

Skullcap \Skull"cap`\, n.
   1. A cap which fits the head closely; also, formerly, a
      headpiece of iron sewed inside of a cap for protection.

   2. (Bot.) Any plant of the labiate genus {Scutellaria}, the
      calyx of whose flower appears, when inverted, like a
      helmet with the visor raised.

   3. (Zo["o]l.) The Lophiomys.

   {Mad-dog skullcap} (Bot.), an American herb ({Scetellaria
      lateriflora}) formerly prescribed as a cure for
      hydrophobia.

Source : WordNet®

mad-dog skullcap
     n : an American mint that yields a resinous exudate used
         especially formerly as an antispasmodic [syn: {blue
         pimpernel}, {blue skullcap}, {mad-dog weed}, {Scutellaria
         lateriflora}]