A term used on reddit to describe a post or comment intentionally designed to illicit a large number of upvotes; often centered around a currently popular theme.
My dad died today, here is a picture of him with Neil deGrasse Tyson and me as a baby. All aboard the karma train! choo choo!
the cumulative karma one builds up, either good or bad, through actions. karmic lessons are sometimes carried into the future, even into future lives, so karma keeps building. The karmatrain is the route you are on.
That driver cut me off! That's okay, cause his karmatrain will catch up with him later.