This is a sexual act where 2 or more men have sex with a black woman at the same time. Many refer to 2 men having sex with a female at the same time as 'Running a Train,' hence the name since it pertains to the same act with a black female. The black woman who is part of the act can then be refered to thereafter as a 'Harriet Tubman'. (See Hariet Tubman). This act can be performed anywhere.
Billy: Yo last night me and Bobby had an underground railroad with that black girl Marissa.
Ralph: What do you mean?
Billy: We were chillin in my car & she started sucking my dick when Bobbby was fucking her from behind.
Ralph: Totally Awesome!
Billy: Yea, I changed her name in my phone to Harriet Tubman
The route, or system of back streets taken when you want to avoid the main arterial roads and heavily trafficked areas of your Town/Municipality in order to ride dirty.
Tubman: Wanna smoke this blunt in the car?
Truth: Hell yeah Tubman: Wanna smoke this blunt on the way to Taco Bell?
Truth:Yes, but lets take the underground railroad, cops are out in full force Friday night.
Was neither underground nor a railroad. It was the different ways that Southern slaves escaped their masters by getting help from abolitionists to lead them to freedom in the North. Made famous by Harriet Tubman.