Douglas Harper's Etymology Dictionary
1779, from French coup de foudre, literally "stroke of lightning," also "love at first sight" (see coup).
Wiktionary
n. A sudden unexpected event, especially an emotional one; love at first sight.
Usage examples of "coup de foudre".
Gently turningMiss Charing to face the mirror again, she pointed out to herthe many excellencies of the gown, and in a spate of volubilitycontrived to say that it was more economical to purchaseone expensive dress than three cheaper ones, that the sight ofmademoiselle in such a toilette must infallibly strike thebeholder like a coup de foudre, that she believed she hadconfused its price with that of the cerulean blue satin whichhad not become mademoiselle, and, finally, that to oblige sogood a customer as miladi she would make a reduction.
I had fallen in love with Elaine instantly, smitten by le coup de foudre.