Originally the term 'spitebomb' meant to multiply downvote a post on a website which uses up/downvoting. The spitebombing was usually done because the poster was unpopular (and often by a clique of attention-whores bearing a private grudge).
The term seems to have originated on the Sparknotes website sometime in 2002.
Both the term, and the practice, are now regularly seen on other websites.
I see your post has attracted fifteen anonymous downvotes. Are you spitebombing yourself to attract attention?