What is meant by "bumping" a thread in message boards?

Question

Some message boards threads are titled "Bump this thread." I have no idea what it means.

Answer 1

A lot of message boards (possibly MOST) are reverse chronologically sorted.

The threads most recently added to are at the top.

If someone doesn't want a thread to be buried, they'll add to it, just to "bump" it back up to the top.

Answer 2

it's when no one has made a post to the thread in a while and then someone makes a post and it moves back up the list of threads again.