What is 3-3-7?
Similar to "talk to the hand".
Comes to us from voicemail systems. If you're listening to a long message that you don't care about, you hit 3-3 to fast forward to the end and "7" to delete. So to "3-3-7" someone is to basically ignore what the person is saying.
John wanted to have a long discussion with me about the benefits of vinyl windows vs. wood windows, but I gave him the 3-3-7.