(of a person, animate object following “with”) To come to have feelings of love directed at another person or a thing.
I fell in love with him the moment I first saw him.
To come to have feelings of love towards each other.
They met, fell in love, got married, and lived happily ever after.
(of a person, inanimate object following “with”) To come to have feelings of intense liking directed at another person or a thing.
I have just fallen in love with Rome!