The Collaborative International Dictionary of English v.0.48:

Alpaca \Al*pac"a\, n. [Sp. alpaca, fr. the original Peruvian
   name of the animal. Cf. Paco.]
   1. (Zool.) An animal of Peru (Lama paco), having long,
      fine, wooly hair, supposed by some to be a domesticated
      variety of the llama.
      [1913 Webster]

   2. Wool of the alpaca.
      [1913 Webster]

   3. A thin kind of cloth made of the wooly hair of the alpaca,
      often mixed with silk or with cotton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

alpaca
    n 1: wool of the alpaca
    2: a thin glossy fabric made of the wool of the Lama pacos, or
       made of a rayon or cotton imitation of that wool
    3: domesticated llama with long silky fleece; believed to be a
       domesticated variety of the guanaco [syn: alpaca, Lama
       pacos]