Definitions of teaser:

• noun:   a device for teasing wool

  Example: "A teaser is used to disentangle the fibers"

• noun:   an attention-getting opening presented at the start of a television show
• noun:   an advertisement that offers something free in order to arouse customers' interest
• noun:   a worker who teases wool
• noun:   someone given to teasing (as by mocking or stirring curiosity)
• noun:   a flat at each side of the stage to prevent the audience from seeing into the wings
• noun:   a particularly baffling problem that is said to have a correct solution