thermal

1 of 2

adjective

ther·​mal ˈthər-məl 

1

a

: of, relating to, or caused by heat

thermal stress

thermal insulation

b

: being or involving a state of matter dependent upon temperature

thermal conductivity

thermal agitation of molecular structure

c

: having low energies of the order of those due to thermal agitation

thermal neutrons

2

: designed (as with insulating air spaces) to prevent the dissipation of body heat

thermal underwear

3

[Latin thermae public baths, from Greek thermai, plural of thermē] : of, relating to, or marked by the presence of hot springs

thermal waters

thermally

ˈthər-mə-lē 

adverb

thermal

2 of 2

noun

: a rising body of warm air

Did you know?

In days gone by, much of the male population of the northern states in the cold months would wear a garment of thermal underwear covering the entire body, called a union suit. Union suits kept sodbusters, cowboys, and townsfolk alike not only warm but also itchy and a little on the smelly side (back when bathing once a week was considered the height of cleanliness). Thermal imaging is photography that captures "heat pictures"--rather than ordinary light pictures--of objects. And thermal pollution occurs when industrial water use ends up warming a river in a damaging way. Small-plane pilots use thermal as a noun for a warm updraft, often over a plowed field or desert, that lifts their wings, just as it enables hawks to soar upward without moving their wings.

Examples of thermal in a Sentence

Recent Examples on the Web

Adjective

While Idaho doesn’t specifically address the use of thermal and night-vision devices while hunting, other states have prohibited their use for either hunting or game retrieval. —Andrew McKean, Outdoor Life, 10 Jan. 2025

Buying them a thermal cat bed or a sweater is a great idea to help them through the winter. —Paul Du Quenoy, Newsweek, 10 Jan. 2025

Noun

The thermals have been redesigned (including an additional heat pipe for the CPU and GPU) to maximize power while aiming to keep heat and noise lower, a goal that reflects user feedback. —Matthew Buzzi, PCMAG, 7 Jan. 2025

Start with this trendy quarter-zip thermal as your go-to base layer. —Taylor Jean Stephan, People.com, 25 Dec. 2024

Word History

Etymology

Adjective

Greek thermē

First Known Use

Adjective

1742, in the meaning defined at sense 3

Noun

1933, in the meaning defined above

Phrases Containing thermal

• British thermal unit
• long/thermal underwear
• thermal pollution
• thermal printer

Kids Definition

thermal

1 of 2 adjective

ther·​mal ˈthər-məl 

1

: of or relating to a hot spring

thermal springs

2

: of, relating to, caused by, or saving heat

thermal energy

thermal underwear

thermally

-mə-lē 

adverb

thermal

2 of 2 noun

: a rising body of warm air

Medical Definition

thermal

adjective

ther·​mal ˈthər-məl 

1

: of, relating to, or caused by heat

tactile and thermal senses

2

: being or involving a state of matter dependent upon temperature

thermal agitation of molecular structure

thermally

-mə-lē 

adverb