The Collaborative International Dictionary of English v.0.48:

Myrtle \Myr"tle\ (m[~e]r"t'l), n. [F. myrtil bilberry, prop., a
   little myrtle, from myrte myrtle, L. myrtus, murtus, Gr.
   my`rtos; cf. Per. m[=u]rd.] (Bot.)
   A species of the genus Myrtus, especially Myrtus
   communis. The common myrtle has a shrubby, upright stem,
   eight or ten feet high. Its branches form a close, full head,
   thickly covered with ovate or lanceolate evergreen leaves. It
   has solitary axillary white or rosy flowers, followed by
   black several-seeded berries. The ancients considered it
   sacred to Venus. The flowers, leaves, and berries are used
   variously in perfumery and as a condiment, and the
   beautifully mottled wood is used in turning.
   [1913 Webster]

   Note: The name is also popularly but wrongly applied in
         America to two creeping plants, the blue-flowered
         periwinkle and the yellow-flowered moneywort. In the
         West Indies several myrtaceous shrubs are called
         myrtle.
         [1913 Webster]

   Bog myrtle, the sweet gale.

   Crape myrtle. See under Crape.

   Myrtle warbler (Zool.), a North American wood warbler
      (Dendroica coronata); -- called also myrtle bird,
      yellow-rumped warbler, and yellow-crowned warbler.

   Myrtle wax. (Bot.) See Bayberry tallow, under Bayberry.


   Sand myrtle, a low, branching evergreen shrub (Leiophyllum
      buxifolium), growing in New Jersey and southward.

   Wax myrtle (Myrica cerifera). See Bayberry.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Leiophyllum buxifolium
    n 1: low-growing evergreen shrub of New Jersey to Florida grown
         for its many white star-shaped flowers and glossy foliage
         [syn: sand myrtle, Leiophyllum buxifolium]