A sock puppet or other member of an online community such as Amazon forums that liberally, and obsessively gives unhelpful votes to discussion participants. A negginator rarely posts why they voted no, and often posts unhelpful votes in bulk to all forum participants, or singles out a single poster for negative voting.
Forum poster Adam posts his opinion, and nine other forum participants post their opinion as well. The negginator comes in and posts an unhelpful vote on every posting. In conjunction with sock puppets, even more negative votes get posted in unison.