"The man who had contradicted him had no titles. That was why he had called him a woman. Okonkwo knew how to kill a man's spirit."
Igbo Women
Public DomainIgbo Women - Credit: Wikispaces

Women are considered to be of a low status in Igbo society; therefore, this is an incedible insult made by Okonkwo. See an essay here on the consequences of inferiorization of Igbo women.