supercool

To cool (a substance) below a phase-transition temperature without the transition occurring; for example, to cool a gas below the boiling point without condensation or to cool a liquid below the freezing point without solidification.

To become supercooled.

To cool (a liquid) below its freezing-point without producing solidification. Also overcool and undercool.

To cool a material below its transition temperature without that transition occurring

Very cool; thoroughly excellent, relaxed, or fashionable.