姑父 refers to one's father's sister's husband.
Topic 1.1: 1.1 Families and Communities in China
姑父 (gūfu) cheat sheet for homework
姨妈 (yímā): One's mother's sister.
阿姨 (āyí): A general term for aunt or any woman who is older than you but not old enough to be called "grandma."
叔叔 (shūshu): One's father's younger brother.