Merriam-Webster Collegiate Dictionary - kingdom

 noun  Date: before 12th century  1. archaic kingship  2. a politically organized community or major territorial unit having a monarchical form of government headed by a king or queen  3. often capitalized  a. the eternal kingship of God  b. the realm in which God's will is fulfilled  4.  a. a realm or region in which something is dominant  b. an area or sphere in which one holds a preeminent position  5.  a. one of the three primary divisions into which natural objects are commonly classified — compare animal ~, mineral ~, plant ~  b. a major category (as Plantae or Protista) in biological taxonomy that ranks above the phylum and below the domain