The Collaborative International Dictionary of English v.0.48:

Teaser \Teas"er\, n.
   1. One who teases or vexes.
      [1913 Webster]

   2. (Zool.) A jager gull. [Prov. Eng.]
      [1913 Webster]

   3. (Elec.) A shunt winding on field magnets for maintaining
      their magnetism when the main circuit is open.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

teaser
    n 1: a worker who teases wool
    2: someone given to teasing (as by mocking or stirring
       curiosity) [syn: tease, teaser, annoyer, vexer]
    3: an advertisement that offers something free in order to
       arouse customers' interest
    4: a particularly baffling problem that is said to have a
       correct solution; "he loved to solve chessmate puzzles";
       "that's a real puzzler" [syn: puzzle, puzzler,
       mystifier, teaser]
    5: an attention-getting opening presented at the start of a
       television show
    6: a flat at each side of the stage to prevent the audience from
       seeing into the wings [syn: tormenter, tormentor,
       teaser]
    7: a device for teasing wool; "a teaser is used to disentangle
       the fibers"

Moby Thesaurus II by Grady Ward, 1.0:

129 Moby Thesaurus words for "teaser":
   Artful Dodger, Casanova, Circe, Don Juan, Gordian knot, Lorelei,
   Machiavel, Machiavelli, Machiavellian, Parthenope, Siren, act drop,
   actor, annoyer, asbestos, asbestos board, backdrop, badgerer,
   bamboozler, batten, befuddler, beguiler, border, bully, charmer,
   cloth, coquette, coulisse, counterfeiter, counterweight, crux,
   curtain, curtain board, cyclorama, deceiver, decor, deluder,
   dilemma, dissembler, dissimulator, dodger, double-dealer, drop,
   drop curtain, duper, ecdysiast, enchanter, enchantress, enigma,
   enticer, entrancer, faker, femme fatale, fire curtain, flat,
   flipper, flirt, fooler, forger, gay deceiver, hanging, harasser,
   harrier, heckler, hoaxer, hypnotizer, inveigler, jilt, jilter,
   joker, jokester, kidder, knot, knotty point, leg-puller,
   mesmerizer, misleader, nag, node, nodus, nonplus, nudnik, nudzh,
   oxymoron, paradox, peeler, perplexity, persecutor, pest, pesterer,
   plagiarist, plagiarizer, plaguer, playactor, pons asinorum, poser,
   practical joker, puzzle, quandary, rag, ragger, role-player,
   sadist, scene, scenery, screen, seducer, seductress, side scene,
   siren, spoofer, stage screw, stripper, striptease, tab, tableau,
   tease, tempter, temptress, torment, tormentor, transformation,
   transformation scene, vamp, vampire, vexed question, wing, wingcut,
   woodcut