Dictionary.com defines "Gimmick" as follows:
noun1. An ingenious or novel device, scheme, or stratagem, especially one designed to attract attention or increase appeal.2. A concealed, usually devious aspect or feature of something, as a plan or deal: An offer that good must have a gimmick in it somewhere.3. A hidden mechanical device by which a magician works a trick or a gambler controls a game of chance.
“The question is, of course, what kind of interesting and new boss fights can you have without resorting to gimmicks like Rhyolith’s steering or Zon’ozz’s bouncing? It’s not that all gimmick fights are bad, but Yor’sahj, for example, was (IMHO) an inventive fight that wasn’t really based on some new-fangled gimmick.”
|Sha of Pride Pride Bar. Get that baby to 100, and you're pretty much dead.|
|Opportunistic Strike! Dance, and then BAM!|
gim·mick [gim-ik]noun4. In the context of a video game boss, anything that changes the default rules of the game, either by granting a new contextual ability (or abilities), redefining what it means for a boss or player to be defeated, or defining a player-induced trigger that alters the currently established rules of combat.