Reference, literal and metaphorically, of a head/top of any item, solid or abstract. The word is commonly used in sexual references, or in non-sexual references that include pentration of a an item or a toxicant entering your body and 'hitting' you quite quickly that it feels like it went straight to your head, or 'dome'
I'll punch you right in the dome.
This bomb-ass shit hitting me righ' quick straight in the dome!
When two or more individuals partake in sexual intercourse with a female. This reference is usually always used to mean such an act, but also can refer to taking a non-stop shit within a toilet, or any other activity that involves a certain degree of persistent that it becomes evident that it takes as long as a train to get the job accomplished.
I was running a train last night on my girlfriend.
"Was Aaron just in the bathroom running a train?"