by 'antha October 11, 2010
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 wnywenke December 13, 2009