Twitterbomb

To pollute the stream of a Twitter hashtag by tweeting a meaningless, satirical, or spamlike tweet containing the hashtag. Usage is comparable to googlebomb.

McDonald's marketers were horrified as #mcdstories, meant to solicit positive tweets about experiences at the restaurant chain, was twitterbombed with replies like "I ate a Big Mac and got the shits for 24hrs. #mcdstories"