Meaning of thermal barrier

ther'mal bar'rier

Pronunciation: [key]
— Aeron., Rocketry. Aeron.,Rocketry.
  1. the high temperatures produced by the friction between a supersonic object and the earth's atmosphere that limit the speed of an airplane or rocket. Also called
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.