Dibs on…
Definition 1 of 1
Pro Tip 1/3Casual Context
Used among friends or informal situations; not suited for formal settings. 
I've got dibs on the front seat for our road trip!
Pro Tip 2/3First Claim
Expresses the desire to claim something first, before anyone else does. 
Just to be clear, I call dibs on the best project topic.
Pro Tip 3/3Not Legally Binding
It's a playful or informal claim, without any legal weight. 
I know you called dibs on that parking spot, but there are no rules here.