Weil's diseasePronunciation: /vʌɪlz/Definition of Weil's disease noun [mass noun] a severe, sometimes fatal, form of leptospirosis transmitted by rats via contaminated water. Origin: late 19th century: named after H. Adolf Weil (1848–1916), German physicianWeil's disease in other Oxford dictionaries Definition of Weil's disease in the US English dictionary