The description of the word you requested from the astronomical dictionary is given below.
hè Magnetis lithos = [Greek] stone of Magnesia
The magnetic field is a force field that is associated with moving electrical charge. A magnetic field can influence electrically charged particles and certain metals by attracting or repulsing them. Almost all solar gas is susceptible to the effects of magnetic field.
Magnetic field behaves as if it is made up of closed magnetic field lines (as you can see if you hold a magnet under a transparent plate with iron filings on it and then gently tap the plate). Magnetic field on the Sun appears to exist in only two forms: either it is so weak that it is swept away by the motion of the solar gas, or it is so strong that it inhibits free motion of the gas (for example in convection). In the latter case, the magnetic field is made up of flux tubes: isolated tube-like things in which the magnetic field is strong, while it is weak or absent outside of the flux tube. Most interesting things on the Sun have something to do with magnetic field: sunspots, pores, plage, filaments, solar flares, and prominences. A famous quote in solar physics, attributed to Robert B. Leighton (around 1970), is
If the Sun didn't have a magnetic field, then it would be as boring as most people think it is.
Solar physicists measure the strength of the magnetic field in units of one gauss (G). The magnetic field of the Earth is at most about 1 G strong. The magnetic field in a sunspot at the solar surface can reach a strength of 3000 G.