Counter-Dibs

The act of reversing a previous "dibs".

John: "Dibs on that piece of pizza"
Emily: "What? No! Counter-Dibs!"

Counter counter dibs

It's just like a counter dibs, but it works on counter dibs, whereas counter dibs only works on dibs.

Joey: Dibs on that last slice of pizza!
Richard: Hell no, counter dibs!
Joey: Counter counter dibs! Now it's mine again!
Richard: :(

Counter dibs shield

A counter dibs shield is a defensive word to counter the attack of a counter dib, therefore, canceling out the counter dib.

(The counter dib shield does not have to be explicitly recited as "counter dib shield", it can also be recited as simply "counter dibs" at the same time someone else is calling a counter dib by saying the same thing.)

Peter: Dibs on the TV!

*At the same time:*
Steve: Counter dibs!
Peter: Counter dibs shield!

Steve: Awh drat!