- a continuous spell of abnormally hot weather
- (not in technical use) an extensive slow-moving air mass at a relatively high temperature
WordReference Random House Unabridged Dictionary of American English © 2020
- Meteorologyan air mass of high temperature covering an extended area and moving relatively slowly.
- Meteorologya period of abnormally hot and usually humid weather.
Collins Concise English Dictionary © HarperCollins Publishers::
heat wave n