thermal

Meanings

1. 1
   adj

   relating to heat, temperature, or the transfer of heat

   The engineer measured the alloy's thermal conductivity at several temperatures.

2. 2
   adj

   designed to reduce heat loss and keep a person or object warm

   The climbers wore thermal underwear beneath their waterproof clothing.

3. 3
   adj

   relating to water naturally heated below Earth's surface, especially a hot spring

   The town developed around a group of mineral-rich thermal springs.

4. 4
   noun

   a rising current or mass of warm air, used by gliders and soaring birds to gain height

   The pilot circled inside a thermal until the glider had gained enough altitude.

Borrowed from French thermal, from New Latin thermalis, based on Greek therme ("heat, warmth"). The earliest English sense concerned hot springs; the word later broadened to anything involving heat and developed the noun for a rising body of warm air.

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