Plain English Meaning
Dangerous weather that isn't caused by thunderstorms — things like heavy icing, strong turbulence, blowing dust or sand, and volcanic ash.
Full Definition
Significant weather phenomena that are not produced by thunderstorm activity, including severe icing, severe or extreme turbulence, dust storms, sandstorms, and volcanic ash, which can hazard aircraft operations and are reported in SIGMETs.
Context Anchor
Seen in SIGMET discussions, where the FAA separates thunderstorm-related from other weather hazards along a .