Definition - What does Ferrofluid mean?
Ferrofluid is a type of fluid that contains suspended micro particles of iron, magnetite or cobalt in a solvent. The solvent is typically an organic fluid as a carrier, or water in some special cases where oil can be dangerous to use (in case of non-volatile, inflammable liquid choices).
Techopedia explains Ferrofluid
Invented in 1963 by NASA's Steve Papell, ferrofluid was created as a liquid rocket fuel for use in space where gravitational pull could not affect fuel in a normal manner. Using a magnetic field, the fuel was to be drawn toward a pump inlet in a weightless environment. Nowadays it is also used in cases such as keeping dust off sensitive hardware such as the drive shafts of magnetic disk drives, as a sealer liquid in the presence of magnetic fields, as well as in the chemical and medical industries. Ferrofluids are superparamagnetic, meaning they are unable to keep their magnetization when not in the influence of a magnetic field.