The Collaborative International Dictionary of English v.0.48:

Flirtation \Flir*ta"tion\, n.
   1. Playing at courtship; coquetry.
      [1913 Webster]

            The flirtations and jealousies of our ball rooms.
                                                  --Macaulay.
      [1913 Webster]

WordNet (r) 3.0 (2006):

flirtation
    n 1: playful behavior intended to arouse sexual interest [syn:
         flirt, flirting, flirtation, coquetry, dalliance,
         toying]

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "flirtation":
   adulterous affair, adultery, affair, agacerie, allure, allurement,
   amorous looks, amour, appeal, attraction, attractiveness,
   beguilement, beguiling, bewitchery, bewitchment, blandishment,
   cajolery, captivation, charisma, charm, charmingness, come-hither,
   come-hither look, coquetry, coquettish glances, coquettishness,
   coyness, cuckoldry, dabbling, dalliance, dallying, enchantment,
   entanglement, enthrallment, enticement, entrapment,
   eternal triangle, fascination, fiddling, flirtatiousness, fooling,
   fooling around, forbidden fruit, forbidden love, glamour,
   goo-goo eyes, hanky-panky, idling, illicit love, inducement,
   infidelity, interest, intrigue, inveiglement, invitation,
   jerking off, kidding around, liaison, loitering, love affair,
   magnetism, messing around, monkeying, monkeying around, ogle,
   piddling, playing, playing around, pottering, puttering, romance,
   romantic tie, seducement, seduction, seductiveness, sex appeal,
   smattering, snaring, tantalization, temptation, tinkering, toying,
   triangle, trifling, unfaithfulness, winning ways, winsomeness,
   witchery, wooing