Wiktionary
ultracold
a. 1 (context physics English) Of a temperature close to absolute zero, especially one at which quantum-mechanical properties are observed. 2 Extremely cold.
Usage examples of "ultracold".
He consists essentially of an inner complex of ultracold neutrons enclosed by an intense magnetic field.
So he resolved to do better on ultracold Jonah 12, where lakes of liquid methane surrounded by icebergs of frozen ammonia gave the planetoid a fairyland appearance.
But after that first momentary shock, the ultrahard logic of his ultracold brain reasserted itself.