What does "bump" mean?

[Michael H. Cothran]

I see it frequently, most recently in the For Sale section. What does it mean?

[francois]

I see it frequently, most recently in the For Sale section. What does it mean?

To bump, in this context, is to add a message to a discussion so it [the discussion] becomes more recent and consequently is listed before other discussions.
In other words, it's a way to promote an old discussion…

[Gary Brown]

Also, anyone subsequently using the “Show unread posts since last visit” feature will see the “bumped” message thread pop up again.

[fike]

An important note:  done excessively, bumping is considered impolite.

[Michael H. Cothran]

Thanks for the explanations. Makes sense now.