1. jack pine slender medium-sized two-needled pine of eastern North America; with yellow-green needles and scaly grey to red-brown fissured bark
  2. Jacobin a member of the radical movement that instituted the Reign of Terror during the French Revolution
  3. Jack Benny United States comedian known for his timeing and delivery and self-effacing humor (1894-1974)
  4. jack bean annual semi-erect bushy plant of tropical South America bearing long pods with white seeds grown especially for forage
  5. jack plane a carpenter's plane for rough finishing
  6. Jacobean of or relating to James I or his reign or times
  7. acapnia a state in which the level of carbon dioxide in the blood is lower than normal; can result from deep or rapid breathing
  8. Jacksonia genus of yellow-flowered Australian unarmed or spiny shrubs without true leaves but having leaflike stems or branches
  9. backbone the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
  10. Jacobite a supporter of James II after he was overthrown or a supporter of the Stuarts
  11. duckpin a bowling pin that is short and squat by comparison with a tenpin
  12. jackpot the cumulative amount involved in a game (such as poker)
  13. Jackson 7th president of the US
  14. alpine relating to or characteristic of high mountains
  15. Alpine relating to the Alps and their inhabitants
  16. Jacobinic of or relating to the Jacobins of the French Revolution
  17. black pine tall symmetrical pine of western North America having long blue-green needles in bunches of 3 and elongated cones on spreading somewhat pendulous branches; sometimes classified as a variety of ponderosa pine
  18. acapnic relating to or demonstrating acapnia
  19. jackknife a large knife with one or more folding blades
  20. jacksnipe a small short-billed Old World snipe

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