|a region in the lee of mountains that receives less rainfall than the region windward of the mountains|
|air pollution containing ozone and reactive chemical compounds formed by sunlight on nitrogen oxides and hydrocarbons, often from auto exhaust|
|1.||Also: thermic of, relating to, caused by, or generating heat or increased temperature|
|2.||hot or warm: thermal baths; thermal spring|
|3.||(of garments or fabrics) specially designed so as to have exceptional heat-retaining properties|
|4.||meteorol a column of rising air caused by local unequal heating of the land surface, and used by gliders and birds to gain height|
|5.||(plural) thermal garments, esp underclothes|
thermal ther·mal (thûr'məl)
Of, relating to, using, producing, or caused by heat.
Intended or designed in such a way as to help retain body heat.
|thermal (thûr'məl) Pronunciation Key
Adjective Relating to heat.
Noun A usually columnar mass of warm air that rises in the lower atmosphere because it is less dense than the air around it. Thermals form because the ground surface is heated unevenly by the Sun. The air usually rises until it is in equilibrium with the air surrounding it.