supercool

UK: /ˌsuːpəˈkuːl/ US: (so̅o̅′pər ko̅o̅l′)

WordReference Random House Unabridged Dictionary of American English © 2025

su•per•cool  (so̅o̅′pər ko̅o̅l′), v.t. 

1. Physics to cool (a liquid) below its freezing point without producing solidification or crystallization;
   undercool.

v.i. 

2. Physics to become supercooled.

adj. 

3. very cool in temperature, esp. of the maximum coolness possible: used as a setting on air conditioners.
4. Slang Terms very cool;
   very sophisticated, up-to-date, unemotional, etc.

• super- + cool 1905–10

Collins Concise English Dictionary © HarperCollins Publishers::

supercool / ˌsuːpəˈkuːl/ verb

1. to cool or be cooled without freezing or crystallization to a temperature below that at which freezing or crystallization should occur. Supercooled liquids are not in equilibrium