The Jargon File (version 4.4.7, 29 Dec 2003):

honey pot
 n.

    1. A box designed to attract crackers so that they can be observed in
    action. It is usually well isolated from the rest of the network, but has
    extensive logging (usually network layer, on a different machine).
    Different from an iron box in that its purpose is to attract, not merely
    observe. Sometimes, it is also a defensive network security tactic ? you
    set up an easy-to-crack box so that your real servers don't get messed
    with. The concept was presented in Cheswick & Bellovin's book Firewalls and
    Internet Security.

    2. A mail server that acts as an open relay when a single message is
    attempted to send through it, but discards or diverts for examination
    messages that are detected to be part of a spam run.