The Collaborative International Dictionary of English v.0.48:

Pansy \Pan"sy\, n.; pl. Pansies. [F. Pens['e]e thought, pansy,
   fr. penser to think, L. pensare to weigh, ponder. See
   Pensive.] (Bot.)
   A plant of the genus Viola (Viola tricolor) and its
   blossom, originally purple and yellow. Cultivated varieties
   have very large flowers of a great diversity of colors.
   Called also heart's-ease, love-in-idleness, and many
   other quaint names.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Heart's-ease \Heart's"-ease`\ (h[aum]rts"[=e]z`), n.
   1. Ease of heart; peace or tranquillity of mind or feeling.
      --Shak.
      [1913 Webster]

   2. (Bot.) A species of violet (Viola tricolor), a common
      and long cultivated European herb from which most common
      garden pansies are derived; -- called also pansy.
      [WordNet sense 1]

   Syn: wild pansy, Johnny-jump-up, heartsease,
        love-in-idleness, pink of my John, Viola tricolor.
        [1913 Webster + WordNet 1.5]

   3. (Bot.) A violet of the Pacific coast of North America
      (Viola ocellata) having white petals tinged with yellow
      and deep violet. [WordNet sense 2]

   Syn: two-eyed violet, heartsease, Viola ocellata.
        [WordNet 1.5]

   4. (Bot.) A common Old World viola (Viola arvensis) with
      creamy often violet-tinged flowers. [WordNet sense 3]

   Syn: field pansy, heartsease, Viola arvensis.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

heartsease
    n 1: a common and long cultivated European herb from which most
         common garden pansies are derived [syn: wild pansy,
         Johnny-jump-up, heartsease, love-in-idleness, pink
         of my John, Viola tricolor]
    2: violet of Pacific coast of North America having white petals
       tinged with yellow and deep violet [syn: two-eyed violet,
       heartsease, Viola ocellata]
    3: common Old World viola with creamy often violet-tinged
       flowers [syn: field pansy, heartsease, Viola arvensis]
    4: the absence of mental stress or anxiety [syn: peace,
       peacefulness, peace of mind, repose, serenity,
       heartsease, ataraxis]