The Collaborative International Dictionary of English v.0.48:

chive \chive\, chives \chives\, n. [F. cive, fr. L. cepa, caepa,
   onion. Cf. Cives, Cibol.] (Bot.)
   A perennial plant (Allium Schoenoprasum), allied to the
   onion, having hollow cylindrical leaves used for seasoning.
   The young leaves are used in omelets, etc. [Written also
   cive.]

   Syn: chive, cive, schnittlaugh, Allium schoenoprasum.
        [1913 Webster]

   2. the bulbous herb Allium Schoenoprasum used fresh as a
      mild onion-flavored seasoning.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

chives
    n 1: perennial having hollow cylindrical leaves used for
         seasoning [syn: chives, chive, cive, schnittlaugh,
         Allium schoenoprasum]
    2: cylindrical leaves used fresh as a mild onion-flavored
       seasoning