public domain   n.   Land owned and controlled by the state or federal government. The status of publications, products, and processes that are not protected under patent or copyright.

Main Entry: public do·main
Pronunciation: -dO-'mAn
Function: noun
1 : land owned directly by the government
2 : the realm or status of property rights that belong to the community at large, are unprotected by copyright or patent, and are subject to appropriation by anyone

public domain
(PD) The total absence of copyright protection. If something is "in the public domain" then anyone can copy it or use it in any way they wish. The author has none of the exclusive rights which apply to a copyright work.
The phrase "public domain" is often used incorrectly to refer to freeware or shareware (software which is copyrighted but is distributed without (advance) payment). Public domain means no copyright -- no exclusive rights. In fact the phrase "public domain" has no legal status at all in the UK.
See also archive site, careware, charityware, copyleft, crippleware, guiltware, postcardware and -ware. Compare payware.