n. Common occurrence at raves, shows or other mass gatherings of people. When a group of people hold hands (or simply follow each other) to move through a crowd single-file so as to not lose track of each other and also to clear a path for those behind.
Human trains are either viewed as extremely annoying or very beneficial.
Dude, I was at a concert and had a perfect spot up close when a human train of tall assholes wedged their way through and came to a halt right in front of me!
I was up front at a rave and had to piss so bad I was thinking about going in my pants, when a human train passed by so I latched on and swiftly made my way out of the crowd.