Shortwave

Also known as Shortwave Trough; a disturbance in the mid or upper part of the atmosphere which induces upward motion ahead of it. If other conditions are favorable, the upward motion can contribute to thunderstorm development ahead of a shortwave.

In radio communications, pertaining to the band of frequencies approximately between 3 MHz and 30 MHz. Note: "Shortwave" is not a term officially recognized by the international community.