1.nounThe realm of intellectual property which is not protected by patents or copyright, i.e. over which no person or other legal entity can establish a proprietary interest.
"There is very little information about the treaty which is in the public domain."
2.nounOpen land such as unowned prairie in the western and southwestern United States; space not subject to a land patent.
3.nounThe realm of published works, as opposed to unpublished tracts.