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):

Viola arvensis
    n 1: common Old World viola with creamy often violet-tinged
         flowers [syn: field pansy, heartsease, Viola
         arvensis]