What to call your maternal uncle's daughter?

Answer 1

Your uncle's daughter is your first cousin. In the English language, it does not matter whether the uncle is a maternal uncle or a paternal uncle. All the children of your aunts and uncles are your first cousins.

Answer 2

Your uncle's daughter is your first cousin.

Answer 3

Your cousin! =) (Or by his/her first name =P)
Your uncle's child is your cousin

Answer 4

Your grand uncle's (or great uncle's) daughter and one of your parents are first cousins to each other. So you and your grand uncle's daughter are first cousins, once removed, to each other.