Genevieve G. answered 08/08/19
Ivy+ & Iowa grad/UGA PhD for writing, editing, proofreading
The word you're referring to is dibs. Here's the entry for it in the Oxford English Dictionary (the bible of the English language):
"A children's word used to express a claim or option on some object (frequently int.); chiefly in to get (etc.) dibs on (something), to have first claim to. U.S. colloquial."
Basically, it's a colloquial or slang word in American English meaning you claim something for yourself. You'll often hear it with the verb call: "I call dibs on the first pancake!" (say you want the first greasy pancake) or "Dibs on shotgun!" (say you want to ride in the passenger seat of the car).
Everyone respects dibs. You call it, you got it!