1. Any of several medical techniques that use cold for therapeutic purposes; such as, using ice to deaden pain.
2. The study or practice of keeping a newly dead body at an extremely low temperature in the hope of restoring it to life later with the help of future medical advances: The process of cryonics involves replacing the blood with an anti-freeze fluid, slowly cooling the body to -70C, and then packing it in dry ice to be transported to a storage facility.

The scientific theory underlying cryonics is theoretical or hypothetical and controversial, and there is a great deal of disagreement about its ethical implications.