I just say “cousin’s cousin”. What’s your family’s word for it?
We call them “Turkey Cousins”, largely because the group of such cousins to which we’re closest are a bunch of turkeys. It’s a surprisingly useful term. Then again, my extended family is large enough that being able to keep track of relationships is a survival trait.
My mother used this term with the similar “relations” on my dad’s side of the family, that they were the “outlaws.” I default to “____-in-law” when it doesn’t matter if I distinguish the lack of blood relation.
My mother is my sister-in-law’s suegra; SiL’s-Mom is my brother’s suegra. Mom and SiL’s-Mom are each other’s consuegras.
In my father’s family, anybody who’s joined the clan by marriage is referred to as “los agregados a la banda,” lit. “those who have been added to the band.” That means my mother, her parents and sister, my uncles’ wifes, my paternal aunt’s husband… cos yeah, they’re part of the clan but there’s some things those born to the clan do which leave “the added ones” scratching their heads in confusion no matter how long it’s been since they got added.
I would say “sister-in-law by marriage” indicating that you have no direct blood family ties to the relationship.
This is why the term “shirt-tail relative” was invented.