| 1. | Also called sonic barrier, transonic barrier. (not in technical use) a hypothetical barrier to flight beyond the speed of sound, so postulated because aircraft undergo an abruptly increasing drag force induced by compression of the surrounding air when traveling near the speed of sound. |
| 2. | break the sound barrier, to travel faster than the speed of sound. |

The sudden increase in air resistance that occurs when an aircraft approaches the speed of sound. This is also called the sonic barrier.
| sound barrier
The sharp increase in drag experienced by aircraft approaching the speed of sound. Also called sonic barrier. |