Short for a dick queef. This is typically achieved when a smaller dick goes into a bigger dick's dickhole. When the smaller dick exits quickly, a popping noise is made: the deef.
Don't pull out your pencil dick out of this elephant trunk too quick or we'll deef.
Man, that deef was so loud my neighbours down the street called the cops, complaining about gun shots.
Oh my god, she just blew into my peehole and it made me deef in her mouth.
Bro, I was in the middle of a presentation when I deefed so hard I blew a hole in my underwear.