This is an irregular feature - both in frequency and oddness - dedicated to a word I came across that I have never previously used.
magnetohydrodynamic - adj.. pertaining to a method of directly generating electricity by passing an ionized gas through a magnetic field at extremely high temperatures.
A magnetohydrodynamic drive (also known as an "MHD propulsor"), is an experimental method for propelling seagoing vessels. Electric currents are passed through seawater in the presence of a massive magnetic field.
The primary drawback with MHD technologies in seagoing vessels is that they are more expensive than a conventional propeller driven by an engine. Some suggest that fuel cell technology may make MHD systems competitive with conventional means of propelling watercraft.
MHD systems are also being considered for the propulsion of spacecraft, using plasma or a thin cloud of ionic gasses. One of the most revolutionary of these systems is the variable specific impulse magnetoplasma rocket, the physics of which are far beyond my capabilities to explain; I'm just a word guy.