I don't think there is a real "definition" of love. Scientifically speaking, love is a bunch of chemicals in our brains to ensure continuation of the human species by bonding two humans closely enough to be able to reproduce and raise their young.
If you're thinking along the lines of action, well, then there's definitely no clear definition. I'm sure we're all familiar with everyone's different love languages. Some are bold and explicit, while others are subtle and only lukewarm. For example, I'm more of an explicit lover, I need to tell the people I love that I love them a hundred times a day, and I need to hug them and kiss them and, you know, just do things for them. On the other hand, my boyfriend's a quieter kind of lover. He doesn't say "I love you" back as often as I'd like him too, he's sooooo bad at reassuring me that he loves me, but to him his love should be like air; it's just there. He does little things like give me the best part of the chicken, shield me from the rain, those little, seemingly insignificant things that he'd do only for me.
Love is everywhere. My favourite romcom is Love Actually, and if you haven't seen it, it starts out by showing short clips of people meeting after a long time at the airport pickup area, which actually made me tear because... it was during a time I was trying so hard to believe in the existence of love, and that just showed me love did exist. Love is everywhere. It's in the little expressions like donating money to the needy, when your colleague buys you coffee just because, when your SO cuddles with you in bed watching a good movie, or even on this site where people actively try to help others.
Love is the thread of our indispensable social fabric.
Wow, this was a really long answer. Haha! In any case, trust me when I say that you know love when you feel it. That teeny little glow in your heart that makes you smile when you think about it, you know? Everyone's in love, and everyone loves; love truly is everywhere.