What does bump up mean?

People keep posting it on threads?...
Posted via Mobile Device

It's to bring their thread back up to the first page.

Some people do it openly by posting 'bump', while others are sneaky about it, and pretend someone asked them something.

Ohhh
Posted via Mobile Device

More commonly seen in the ads section, or a post that no one has responded too within a few hours.

B-ring
U-p
M-y
P-ost

;)
Posted via Mobile Device