The Collaborative International Dictionary of English v.0.48:

madagascar periwinkle \madagascar periwinkle\ n. (Bot.)
   A commonly cultivated Old World woody herb (Vinca rosea)
   having large pinkish to red flowers.

   Syn: periwinkle, rose periwinkle, Madagascar periwinkle, old
        maid, Cape periwinkle, red periwinkle, cayenne jasmine,
        Catharanthus roseus, Vinca rosea.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Madagascar periwinkle
    n 1: commonly cultivated Old World woody herb having large
         pinkish to red flowers [syn: periwinkle, rose
         periwinkle, Madagascar periwinkle, old maid, Cape
         periwinkle, red periwinkle, cayenne jasmine,
         Catharanthus roseus, Vinca rosea]