NOUN (2)

1. an area where everything is visible;

2. a circular prison with cells distributed around a central surveillance station; proposed by Jeremy Bentham in 1791;

The Collaborative International Dictionary of English v.0.48:

Panopticon \Pa*nop"ti*con\, n. [NL. See Pan-, and Optic.]
   [1913 Webster]
   1. A prison so contructed that the inspector can see each of
      the prisoners at all times, without being seen.
      [1913 Webster]

   2. A room for the exhibition of novelties.
      [1913 Webster]

WordNet (r) 3.0 (2006):

panopticon
    n 1: an area where everything is visible
    2: a circular prison with cells distributed around a central
       surveillance station; proposed by Jeremy Bentham in 1791