I spent all that time trying to get through to you. Dean calls once, and now it's, 'Hello'?!
Sam: So, what, you -- you like him better or something?
Castiel: Dean and I do share a more profound bond. I wasn't gonna mention it.
Cas, I think what he's trying to say is that... he went to Hell for us. I mean, he really took one for the team. You remember that? And then he comes back without a clue, and you can't take five friggin' minutes to give him some answers?
Profound Bond has become short-hand in fandom for Dean and Castiel's relationship - whether platonic or romantic.
Profound Bond is also a website focusing on Destiel including fanfic, vids, meta, and forums.