a. [ Gr. &unr_; thoroughly warm; dia` through + &unr_; warm, hot. Cf. Diathermous. ] Freely permeable by radiant heat.

a. Warm-blooded; homoiothermal. [ 1913 Webster ]

a. (Zool.) Warm-blooded; hematothermal. [ R ] [ 1913 Webster ]

a. Warm-blooded. [ 1913 Webster ]

adj. (Biol.) having constant and relatively high body temperature; warm-blooded; same as homoiothermal; -- of birds and mammals. Contrasted to poikilothermal.
Syn. -- homoiothermic, homoiothermal, homothermic, homothermal. [ WordNet 1.5 ]

a. See Homoiothermal. [ 1913 Webster ]

a. [ Gr. &unr_; like + E. thermal. ] (Physiol.) Maintaining a uniform body temperature, usually above the ambient temperature; hæmatothermal; homothermic; warm-blooded; -- applied to warm-bodied animals such as birds and mammals, because they maintain a nearly uniform temperature in spite of the great variations in the surrounding air; in distinct from the cold-blooded (poikilothermal) animals, whose body temperature follows the variations in temperature of the surrounding medium.
Syn. -- homeothermal, homeothermic, homothermal, homothermic, homoiothermic. [ 1913 Webster ]

a. [ Hydro-, 1 + thermal. ] 1. Of or pertaining to hot water; -- used esp. with reference to the action of heated waters in dissolving, redepositing, and otherwise producing mineral changes within the crust of the globe. [ 1913 Webster ]

2. of, pertaining to, or using the hot waters or steam found at special locations within the earth's crust; as, hydrothermal power generation. [ PJC ]

{ } a. Pertaining to, having the nature of, or marking, isogeotherms; as, an isogeothermal line or surface; as isogeothermal chart. -- n. An isogeotherm. [ 1913 Webster ]

a. [ Cf. F. isotherme. ] (a) Relating to equality of temperature, or an isotherm. (b) (Phys. Geog.) Having reference to the geographical distribution of temperature, as exhibited by means of isotherms; as, an isothermal line; an isothermal chart. [ 1913 Webster ]

Isothermal line. (a) An isotherm. (b) A line drawn on a diagram of energy such that its ordinates represent the pressures of a substance corresponding to various volumes, while the absolute temperature is maintained at a constant value. --
Isothermal zones, spaces on opposite sides of the equator having the same mean temperature, and bounded by corresponding isothermal lines. [ 1913 Webster ]

{ } a. [ Gr. poiki`los changeable + E. thermal, thermic. ] (Physiol.) Having a varying body temperature. See Homoiothermal. [ 1913 Webster ]

a. [ Pref. syn- + thermal. ] Having the same degree of heat. [ 1913 Webster ]

a. [ L. thermae hot springs, fr. Gr. &unr_;, pl. of &unr_; heat, fr. &unr_; hot, warm, &unr_; to warm, make hot; perhaps akin to L. formus warm, and E. forceps. ] 1. Of or pertaining to heat; warm; hot; as, the thermal unit; thermal waters. [ 1913 Webster ]

The thermal condition of the earth. J. D. Forbes. [ 1913 Webster ]

2. caused by or affected by heat; as, thermal springs. [ PJC ]

3. designed to retain heat; as, thermal underwear. [ PJC ]

Thermal conductivity,
Thermal spectrum. See under Conductivity, and Spectrum. --
Thermal unit (Physics), a unit chosen for the comparison or calculation of quantities of heat. The unit most commonly employed is the amount of heat necessary to raise the temperature of one gram or one pound of water from zero to one degree Centigrade. See Calorie, and under Unit. [ 1913 Webster ]

adv. In a thermal manner. [ 1913 Webster ]