表哥 refers to one's older male cousin from the mother's side of the family.
Topic 1.1: 1.1 Families and Communities in China
表哥 (biǎo gē) cheat sheet for homework
表弟 (biǎo dì): One's younger male cousin from the mother's side of the family.
表姐 (biǎo jiě): One's older female cousin from the mother's side of the family.
One's male cousin from the father's side of the family.