Freezing is a type of environmental hazard and damage type. It deals around 10 damage in damage over time, but this can vary. Freezing can be inflicted on other players and enemies with the Kineticore, and you can take freezing damage after spending too much time in cold water, such as most of the water in the 560 period. Enemies (and your player character) taking freeze damage will be tinted a dark blue, and if dead right after or during taking freezing damage, the corpse will be colored dark blue.
Hiro, Mikiko and Superfly all have distinctive responses to taking freeze damage - all different grunts, shudders and teeth chattering.