There are no liquids that are not susceptible to freezing. However, it is feasible to chill a liquid below its typical freezing point under specific conditions. This type of substance is known as a supercooled liquid.
Normal freezing point is the temperature at which a liquid freezes at atmospheric pressure. For a liquid to never freeze, its freezing point must be absolute zero, the lowest temperature that matter can reach: 0 Kelvin or -459.67 degrees Fahrenheit. No such liquid has yet been identified; therefore, all liquids freeze when chilled to a sufficiently low temperature.
At temperatures below its typical freezing point, it is feasible for a liquid to stay liquid. To achieve supercooling, it is necessary to prevent the liquid from nucleating, or generating very minute ice crystals. This can be accomplished by separating the liquid from movement and storing it in a vessel that is thoroughly clean and smooth. Lowering the surrounding pressure while cooling some liquids can also result in supercooling. However, supercooled liquids are extremely unstable and fully freeze once nucleation commences. The nucleation and solidification of supercooled liquid is triggered by a minute flaw or disturbance in the vessel, such as tapping the vessel.