Love is such a used, abused, and misused word that people should possibly stay away from it.
How I would define it?
In essence, love is the basic experience of caring about another, of going out from myself toward the Other.
Love requires caring – not caring about what benefit or enjoyment I can gain from you, but finding joy in the very fact of your existence.
When I say “I love you,” the truthfulness of my statement depends on the size of the “I” and the size of the “you”:
The bigger the “I,” the smaller the love.
But if the “I” is smaller than the “you,” then we have the sense that we are dealing with love.
From a talk by Rabbi Adin Steinsaltz given at Columbia University’s Center for the Study of Science and Religion