1. warm underwear or clothing designed to retain body heat
Usage: plural form
2. rising currents of warm air used by birds and gliders for soaring
Usage: meteorology; aviation

Examples

• She packed her thermals for the skiing trip.
• The wool thermals kept him warm during the winter hike.
• Eagles use thermals to soar high above the mountains.
• The glider pilot searched for thermals to gain altitude.
• Without thermals, the paraglider had to land early.
• His cotton thermals weren’t warm enough for the arctic conditions.