FOUDROYANT/fuːˈdrɔɪənt/
These days, the medical fraternity almost has a monopoly on this word that describes a disease that comes on suddenly and severely (as an alternative to the much more common fulminant, which means the same thing), though only the most academic of clinicians seem to use it.
Outside medicine, it is if anything even more rare, an alternative to words like “brilliant” or “dazzling”, as here in a review in the Minneapolis Star Tribune in 1999: “Heavy on elan and the damper pedal, pianists such as Simon, Earl Wild, Jorge Bolet and Byron Janis wow you with foudroyant playing”.
But anybody with an interest in naval history will know it best as the name for several Royal Navy ships at various periods, such as one of Nelson’s flagships in the Mediterranean in 1799 (a French submarine now has the same name). The word is indeed French, from foudroyer, to strike with lightning, so it makes a very good name for a fighting ship.
