(slang) A man who perceives himself as straight and is the aggressive top in a relationship between two men, especially in prison.
The jocker's sexual behavior can therefore be viewed as situational homosexuality.
2012, "Men Behind Bars: Sexual Exploitation in Prison" By Wayne S. Wooden
More common than the reciprocal and mutually constituted homosexual associations between hoboes were the predatory relationships between older hoboes, or “jockers,” and young initiates, or “punks.”
2010, Citizen Hobo: How a Century of Homelessness Shaped America By Todd DePastino
As the "masculine" or "active" partner in prison sexual exchanges, jockers maintained a sexual identity as heterosexual
2008, Criminal Intimacy: Prison and the Uneven History of Modern American Sexuality by Regina P. Kunzler