a. A form of energy associated with the kinetic energy of atoms or molecules and capable of being transmitted through solid and fluid media by conduction, through fluid media by convection, and through empty space by radiation.
b. The transfer of energy from one body to another as a result of a difference in temperature or a change in phase.
2. The sensation or perception of such energy as warmth or hotness.
3. An abnormally high bodily temperature, as from a fever.
a. The condition of being hot.
b. A degree of warmth or hotness: The burner was on low heat.
a. The warming of a room or building by a furnace or another source of energy: The house was cheap to rent, but the heat was expensive.
b. A furnace or other source of warmth in a room or building: The heat was on when we returned from work.
6. A hot season; a spell of hot weather.
a. Intensity, as of passion, emotion, color, appearance, or effect.
b. The most intense or active stage: the heat of battle.
c. A burning sensation in the mouth produced by spicy flavoring in food.
9. One of a series of efforts or attempts.
a. Sports & Games One round of several in a competition, such as a race.
b. A preliminary contest held to determine finalists.
11. Informal Pressure; stress.
a. An intensification of police activity in pursuing criminals.
b. The police. Used with the.
13. Slang Adverse comments or hostile criticism: Heat from the press forced the senator to resign.
14. Slang A firearm, especially a pistol.
v. heat·ed, heat·ing, heats
1. To make warm or hot.
2. To excite the feelings of; inflame.
3. Physics To increase the heat energy of (an object).
1. To become warm or hot.
2. To become excited emotionally or intellectually.
heat up Informal
To become acute or intense: "If inflation heats up, interest rates could increase" (Christian Science Monitor).
[Middle English hete, from Old English hǣtu; see kai- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.