1. the fundamental distinction, found in most species of animals and plants, based on the type of gametes produced by the individual; also the category to which the individual fits on the basis of that criterion. Called also gender. See also gender identity and gender role.
Underground Railroad. For black slaves in America, the road to freedom was a long and difficult one. The Underground Railroad was, of course, not a railroad at all. It was simply a network of Americans, both black and white, dedicated to destroying the institution of slavery by helping individual slaves escape to freedom.
The Railroad Caboose. For more than a century the railroad caboose was a fixture on the end of freight trains. The real purpose of the caboose was to provide a sheltered vantage point from which trainmen could watch the cars ahead, sleep, cook and eat their meals, and do their paperwork. It served as the working headquarters of the freight conductor and his rear brakeman.