The Collaborative International Dictionary of English v.0.48:

marvel of Peru \marvel of Peru\, marvel-of-Peru \marvel-of-Peru\
   n. (Bot.)
   A common garden plant (Mirabilis jalapa or Mirabilis
   uniflora) of North America having fragrant red or purple or
   yellow or white flowers that open in late afternoon; called
   also four-o'clock. See four-o'clock.

   Syn: common four-o'clock, marvel of Peru, Mirabilis jalapa,
        Mirabilis uniflora.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Mirabilis uniflora
    n 1: common garden plant of North America having fragrant red or
         purple or yellow or white flowers that open in late
         afternoon [syn: common four-o'clock, marvel-of-Peru,
         Mirabilis jalapa, Mirabilis uniflora]