LORELAI: Déjà vu, huh?
RORY: Déjà vu.
Déjà vu, French loanword (literally “already seen”) for the phenomenon of feeling as though one has lived through the present situation before. It is an illusion of memory whereby – despite a strong sense of recollection – the time, place, and context of the “previous” experience are uncertain or impossible. Approximately two-thirds of people report experiencing déjà vu at least once in their lives.
Lorelai and Rory use the word jokingly to refer to the fact that they have each recently caught the other one kissing their boyfriend, causing some awkwardness.
The Annotated Gilmore Girls 