When we hear/say "God is love", what does it mean?

"God is love". I have said this myself many times and I have heard many people in my life say the same thing. So, I am currently meditating on a couple of scripture passages including this one:

So we have known and believe the love that God has for us. God is love, and those who abide in love abide in God, and God abides in them. 
(1 John 4:16)

More on this later, but for now I leave you with the following: when we hear/say "God is love"what does it mean?