thats what i thought at first but that doesnt make sense for where i see it....i mean ill be looking at a bike for sale and someone will just say bump for no reason.
In for sale items, people are doing it (basically posting anything - but they use the term "bump") to move the thread to the top of the list of threads. (You might also see "to the top" or "ttt" - they are doing the same thing - getting the thread to the top of the list, or onto the first page of threads, etc so that it remains very visible). Hope that helps.....