Which term describes a swirly wind phenomenon?

The term that best describes a swirly wind phenomenon is "Tornado." Tornadoes are characterized by their rotating columns of air that form in severe thunderstorms. This rotation occurs due to significant differences in wind speed and direction, leading to the characteristic funnel shape. A tornado is typically a small-scale weather system but can produce highly destructive winds and is often visible due to the debris it picks up.

While both hurricanes and twisters can also involve wind, the specific term "twister" is simply another name for a tornado, so it holds similar meaning, yet may not be as commonly used in formal scientific terminology. Thunderstorms can generate strong winds, but they are broader and encompass various weather phenomena, not exclusively swirling wind patterns. Therefore, "Tornado" is the precise term used to define that specific weather occurrence.