A fever (such as from malaria) that is marked by paroxysms of chills, fever, and sweating recurring at regular intervals. Also a fit of shivering, a chill. Hence, ague can refer to both chills and fevers.
Pronounced 'A-(")gyü with the accent solidly on the "A." "Aigue" entered English usage in the 14th century, having crossed the channel from the Middle French "aguë". The word shares the same origin as "acute." It descends from the Latin "acutus" meaning "sharp or pointed". A "fievre aigue" in French was a sharp or pointed (or acute) fever.