1. polar circle a line of latitude at the north or south poles
  2. color circle a chart in which complementary colors (or their names) are arranged on opposite sides of a circle
  3. Pillars of Hercules the two promontories at the eastern end of the Strait of Gibraltar; according to legend they were formed by Hercules
  4. polar glacier a glacier near the Arctic or Antarctic poles
  5. hour circle a great circle on the celestial sphere that passes through both celestial poles
  6. inner circle an exclusive circle of people with a common purpose
  7. polariscope an optical device used to measure the rotation of the plane of vibration of polarized light
  8. Pericles Athenian statesman whose leadership contributed to Athens' political and cultural supremacy in Greece; he ordered the construction of the Parthenon (died in 429 BC)
  9. in circles without making progress
  10. fairy circle a ring of fungi marking the periphery of the perennial underground growth of the mycelium
  11. parhelic circle a luminous halo parallel to the horizon at the altitude of the sun; caused by ice crystals in the atmosphere
  12. Pleurosorus small genus comprising terrestrial ferns
  13. back circle a feat in which an acrobat arches the back from a prone position and bends the knees until the toes touch the head
  14. pulmonary circulation circulation of blood between the heart and the lungs
  15. Pterocles type genus of the Pteroclididae
  16. great circle a circular line on the surface of a sphere formed by intersecting it with a plane passing through the center
  17. polarize cause to concentrate about two conflicting positions
  18. polar region the part of the Earth's surface forming a cap over a pole
  19. plexus brachialis a network of nerves formed by cervical and thoracic spinal nerves and supplying the arm and parts of the shoulder
  20. polarise cause to concentrate about two conflicting or contrasting positions