Your uncle's daughter is your cousin
In the English language relationship words make no distinction between younger or older siblings. Your mother's brother, whether younger or older, is your uncle and his daughter is your first cousin. His daughter is your mother's niece.
Since the cousin is from your half uncle's wife's side of the family the cousin would not be your cousin.
Your cousin! =) (Or by his/her first name =P)Your uncle's child is your cousin
she would be called your cousin. Maternal uncle's daughter is your cousin.
Your cousin.
Your uncle's first cousin is also your parent's first cousin, and your first cousin, once removed - if your uncle is the brother of one of your parents. Sometimes your uncle is the husband of your parent's sister. Then his cousin in not related to you.
Your first cousin.
Cousin...
Your Cousin
Cousin
Your first cousin.