Bandwagon = Several votes on the same player to try to lynch them. The term is used when votes come in quick succession and without independent reasons. Bandwagons can be especially frustrating for players, because they can seem to build a momentum of their own, often independent of the validity of the original reasoning that started it.
Some players will even give up (either not defend or pull a no contest), rather than face the uphill battle of defending. Bandwagoning is sometimes used on Day 1 to quickly gather information on players' roles and voting patterns. It is especially dangerous during endgame situations where one misvote will make the uninformed majority lose and should be avoided at that point.