The Collaborative International Dictionary of English v.0.48:

Oculus \Oc"u*lus\, n.; pl. Oculi. [L., an eye.]
   1. An eye.
      [1913 Webster]

   2. (Arch.) A round window, usually a small one.
      [1913 Webster]

   3. (Bot.) A leaf bud.
      [1913 Webster]

WordNet (r) 3.0 (2006):

oculus
    n 1: the organ of sight [syn: eye, oculus, optic]