An informal term meaning first right of refusal within a given context. The right of first and exclusive access to some entity, opportunity or reward which is attainable by two or more individuals but is informally claimed or granted to one as a right - usually based on some pretext. The implication is that if the one with 'first dibbs' declines the opportunity, that subsequent individuals with second or third dibbs then inherit that right in turn.

Got the covid-19 vaccine

A variation of dibbs. Dibbs indicates first rights to something and therefore saying "first dibbs" is unecessary and silly. Second dibbs, third, and so on are completely acceptable.