The Ho Train is a figure of speech used for a group of girls that are constantly together and "Ho-ing" around town.
Ex: Doug: Man, can you believe that group of girls that walked into the bar and were trying to get any group of guys to buy them drinks and take them home? What was up with that?
Max: That, my friend, was a Ho Train :(
Ho,
Train,
Ho-ing,
Group of Girls :(