The Collaborative International Dictionary of English v.0.48:

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.
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   2. (Bot.) Any plant of the labiate genus Scutellaria, the
      calyx of whose flower appears, when inverted, like a
      helmet with the visor raised.
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   3. (Zool.) The Lophiomys.
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   Mad-dog skullcap (Bot.), an American herb (Scetellaria
      lateriflora) formerly prescribed as a cure for
      hydrophobia.
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