Definition of public domains:
(n) :
The state of not being owned by anyone, and thus freely usable by everyone.
(n) :
(specifically, law) The realm of intellectual property which is not or no longer protected by copyrights or patents, and thus over which no person can establish a proprietary interest.
(n) :
(especially US) Land regarded as owned by the public, and not subject to a land patent or other forms of private ownership (for example, unowned prairie in the southwestern and western United States).
(n) :
The state of not or no longer being confidential or secret.
(n) :
(also attributively) Often preceded by in the.