IPA: //haɪdrəʊˈmæɡnɛtɪk//
KK: /haɪdroʊmæɡˈnɛtɪk/
Relating to the study of the interaction between magnetic fields and electrically conducting fluids, such as water.
The hydromagnetic effects are important in understanding the behavior of plasma in astrophysical contexts.
Hydromagnetic is formed from "hydro-" (from Greek "hudor", meaning water) and "magnetic" (from Greek "magnetis", meaning of Magnesia, a region known for its magnetic properties). The word refers to the magnetic properties related to water or fluids.
Think of 'water' ('hydro-') and 'magnetism' ('magnetic') together, which helps you remember that hydromagnetic relates to the magnetic effects in water.