thermal

Etymology

From French thermal, from New Latin *thermalis, from Ancient Greek θέρμη (thérmē, “heat”), from Proto-Indo-European *gʷʰer- (“to heat, warm”).

adj

1. Pertaining to heat or temperature.
   Similar studies of rats have employed four different intracranial resorbable, slow sustained release systems—surgical foam, a thermal gel depot, a microcapsule or biodegradable polymer beads. 2013 May-June, Charles T. Ambrose, “Alzheimer’s Disease”, in American Scientist, volume 101, number 3, page 200
2. (fabric) Providing efficient insulation so as to keep the body warm.
3. Caused or brought about by heat.
4. (stone) Having a rough finish by treatment with a blow-torch.

noun

1. (meteorology) A column of rising air in the lower atmosphere created by uneven heating of Earth's surface.
   The hawk had mounted its thermal by the time he got to the yard, flapping its wings violently against the updraft. 2019, Chigozie Obioma, An Orchestra of Minorities, Abacus (2019), page 91

verb

1. (stone) To create a rough finish on stone by treating it with a high-temperature blow-torch.
2. (gliding, often in the present participle) To fly an unpowered aircraft in a (thermal) column of rising air.