WordNet
n. a fan that blows heated air out of the attic of a building
Wikipedia
A powered attic ventilator, or attic fan, is a ventilation fan which regulates the heat level of a building's attic by exhausting hot air. A thermostat is used to automatically turn the fan off and on, while sometimes a manual switch is used. An attic fan can be gable mounted or roof mounted. Additional vents are required to draw in fresh air as the hot air is exhausted. Attic fans are typically used in warmer months, when temperatures in an attic can exceed . A fan may be installed in an attic for the different purpose of cooling a while house, venting hot air out via the attic; such fans are often called whole-house fans.
Usage examples of "attic fan".
I had the attic fan on, and the house was cool, and I dreamed all night.
The wind clattered tinny signs, playing a mean snare on the attic fan.
The house had no air conditioning, but the big attic fan did a good job.