Couster

One's sister and cousin at the same time: the result of either a man producing two children with a set of sisters, or a woman producing two children with a set of brothers, making the female offspring a couster to the other child.

"Carlie is my couster; we have the same Dad but our Moms are sisters. That is, like, so totally freaky!"

by fartknocker101 December 14, 2009

couster

female cousin that is more like a sister

My cousins and sisters are so close we're cousters.

by 'antha October 14, 2010