A windstorm is a stretch of very bad weather where the damage comes from wind, not from water — strong enough to bring down trees and power lines and take tiles off roofs, but with little or no rain. That 'little rain' part is the whole point of the word; if it were pouring, English speakers would just say 'a storm'. So the word is doing a job of contrast: this one was dry, but it still wrecked things. It is much more common in American, Canadian and Australian English than in Britain, where people tend to say 'gales' or 'high winds' instead. You meet it a lot in news reports and, importantly, in insurance documents, where 'windstorm damage' is a defined category that pays out differently from flood damage. It is not a technical meteorological rank like 'typhoon' or 'hurricane' — those have measured wind speeds behind them; 'windstorm' is a general, everyday word covering anything from a rough night to a serious event. In Taiwan a typhoon is the usual picture, but a typhoon brings enormous rain, so it is not really a windstorm.

風暴、強風災（強風但雨不大的暴風天氣）