• noun
• synonym
• antonym

• A-horizon (noun)
  1. the top layer of a soil profile; usually contains humus
• B-horizon (noun)
  1. immediately below the A-horizon; contains deposits of organic matter leached from surface soils
• C-horizon (noun)
  1. beneath the B-horizon and above the bedrock; consisting of weathered rock
• apparent horizon (noun)
  1. the line at which the sky and Earth appear to meet
• artificial horizon (noun)
  1. a navigational instrument based on a gyroscope; it artificially provides a simulated horizon for the pilot
• celestial horizon (noun)
  1. the great circle on the celestial sphere whose plane passes through the sensible horizon and the centre of the Earth
• event horizon (noun)
  1. classically physics a surface beyond which an observer cannot be in contact, esp. a surface round a black hole from which no light can escape from inside
• geological horizon (noun)
  1. especially of fossils a layer of rock with a particular composition ; for dating the stratum
• gyro horizon (noun)
  1. a navigational instrument based on a gyroscope; it artificially provides a simulated horizon for the pilot
• sensible horizon (noun)
  1. the line at which the sky and Earth appear to meet
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