舅舅 refers to one's mother's brother.
舅舅 (jiùjiu) cheat sheet for homework
伯伯 (bóbo): 伯伯 refers to one's father's older brother.
叔叔 (shūshu): 叔叔 refers to one's father's younger brother.
姑姑 (gūgu): 姑姑 refers to one's father's sister.