The Collaborative International Dictionary of English v.0.48:

Playful \Play"ful\, a.
   Sportive; gamboling; frolicsome; indulging a sportive fancy;
   humorous; merry; as, a playful child; a playful writer. --
   Play"ful*ly, adv. -- Play"ful*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

playfully
    adv 1: in a playful manner; "she loosened the half-hoop of
           diamonds on her left hand third finger and held it out to
           him playfully"