Field Inversion was a scientific term to describe when the polarity of a vessel's shield's suddenly, explicable reversed and simply collapsed.
The Cardassian Union developed a weapon that would bring out such an effect on their enemies. Lane Crockett stole the military plans for the weapon and sold it to the Aresians. His theft of the weapon allowed the Aresians to destroy a Galor-class starship, when Crockett's treachery was revealed to Dukat he immediately disintegrated him for his countrymen's deaths. (DS9 - The Secret of the Lost Orb comic: "Gods of War")