(idiomatic) The word love, or an expression of love, usually one that provokes a significant change in a relationship.
“Then take her on a tour of places that are special to the two of you — the bar where you had your first date, the park where you dropped the L-bomb, [...]” 2003, Joe Kita, Guy Q: 1,305 Totally Essential Secrets You Either Know, Or You Don’t, Rodale, →ISBN, page 139: