sunstroke

/ˈsʌnstroʊk/
noun
  1. A serious condition caused by spending too much time in strong sunlight, resulting in fever, headache, and sometimes unconsciousness.
    • Drinking plenty of water can help prevent sunstroke on hot days.
    • The doctor said her dizziness was a mild case of sunstroke.
    • After hiking for hours without a hat, he collapsed from sunstroke.
Synonyms