The Collaborative International Dictionary of English v.0.48:

cilantro \cilantro\ n.
   1. an Old World herb (Coriandrum sativum) with aromatic
      parsleylike leaves and seed.

   Syn: coriander, coriander plant, Chinese parsley, Coriandrum
        sativum.
        [WordNet 1.5]

   2. a parsleylike herb used as seasoning or garnish.

   Syn: coriander, Chinese parsley.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

cilantro
    n 1: Old World herb with aromatic leaves and seed resembling
         parsley [syn: coriander, coriander plant, Chinese
         parsley, cilantro, Coriandrum sativum]
    2: parsley-like herb used as seasoning or garnish [syn:
       coriander, Chinese parsley, cilantro]