[ther.mal] adj [Gk therme] (1756) 1 [L thermae public baths, fr. Gk thermai, pl. of therme]: of, relating to, or marked by the presence of hot springs "~ waters"
2. a: of, relating to, or caused by heat "~ stress" "~ insulation" b: being or involving a state of matter dependent upon temperature "~ conductivity" "~ agitation of molecular structure"
3: designed (as with insulating air spaces) to prevent the dissipation of body heat "~ underwear"
4: having energies of the order of those due to thermal agitation "~ neutrons" -- ther.mal.ly adv
[2]thermal n (1933): a rising body of warm air