from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. See sonic barrier.
  • n. A set of tall wooden, plastic, or concrete barriers placed along a road or highway to muffle the sound of traffic.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The apparent physical boundary (caused by a sudden increase in drag) preventing objects from becoming supersonic.
  • n. A structure beside a highway designed to reduce the noise of traffic.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the increase in aerodynamic drag as an airplane approaches the speed of sound


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