Definition - What does Wilt mean?
Wilt is what occurs when the non-woody parts of a plant lose their rigidity and it begins to droop. Wilt can be the result of environmental conditions, such as a lack of water, or it can be the caused by outside factors or diseases.
In many cases, plant wilt is simply a sign that the plant needs water and its nutritional needs are not currently being met.
MaximumYield explains Wilt
Some plants, like tomatoes, can suffer a wilt that is not environmental, but rather a fungal disease as the result of infected soil or grow media. In a plant suffering from verticillium wilt, leaves will yellow and curl, the plant will wilt, and the stem will be unable to support itself.
Verticillium wilt usually occurs in spring or fall and is treatable with commercial products on the market.
Plants may also wilt when they are under stress during an extended hot spell. They will droop or wilt during the day, but then perk up again as the temperature cools down again at nighttime.
Wilt of this sort usually doesn’t kill a plant, but will hamper its growth as the hot weather continues, and the suffering plant will require extra watering to compensate for the moisture lost from the hot sun.