Definition: Dust storm or sandstorm: An ensemble of particles of dust or sand energetically lifted to great heights by a strong and turbulent wind.
Dust storms or sandstorms generally occur in areas where the ground is covered with loose dust or sand. Sometimes, after having travelled great distances, they may be observed over areas where no dust or sand covers the ground. The forward portion of a dust storm or sandstorm may have the appearance of a wide and high wall that advances fairly rapidly. Walls of dust or sand often accompany a Cumulonimbus that may be hidden by the dust or sand particles. They may also occur without any clouds along the forward edge of an advancing cold airmass.