= property that is owned by all, but its access and use is controlled by the state. An example is a national park. 
From the Wikipedia:
"Public property is property which is owned by the state, city, community or tribe. This is in contrast to private property, owned by a individual person or artificial entities that represent the financial interests of persons, such as corporations. State ownership, also called public ownership, government ownership or state property, are property interests that are vested in the state, rather than an individual or communities." (http://en.wikipedia.org/wiki/Public_property)
"Public property is property, which is dedicated to the use of the public. It is a subset of state property. The term may be used either to describe the use to which the property is put, or to describe the character of its ownership (owned collectively by the population of a state). This is in contrast to private property, owned by a individual person or artificial entities that represent the financial interests of persons, such as corporations. State ownership, also called public ownership, government ownership or state property, are property interests that are vested in the state, rather than an individual or communities." (http://en.wikipedia.org/wiki/Public_property)
At the P2P Foundation, we would tend to use public property, as vested in a state-like entity separate from its individual members, from Common Property, where individual members still directly co-own the resource.
Common Property vs. Public Property
"‘‘Public’’ has been one of those theoretical devices that defined socialist alternative visions in their opposition to capitalism across all theoretical fields, but which was actually a product of eighteenth-century liberal governmentality. ‘‘Public’’ becomes the master signifier of socialism in its opposition to ‘‘private property,’’ but it still carries a reference to ‘‘ownership’’ relations. ‘‘Public property’’ is everyone’s ‘‘capital,’’ but it is still ‘‘capital’’ in the sense that it is a part of the restricted economy and its ‘‘use,’’ or ‘‘productivity,’’ is still restricted with the terms imposed by ‘‘public ownership’’ and limits of the definition of ‘‘public.’’ For example, you may have to be a ‘‘citizen,’’ a ‘‘taxpayer,’’ or even a taxpaying citizen dwelling in a specific neighborhood to use the ‘‘public education’’ provided by the state or city. ‘‘Public’’ never denotes ‘‘everybody’’; it always signifies a limit set by a certain social, linguistic, or jurisprudential criterion, refers exclusively to a specific population. As such, it not only always excludes ‘‘somebody’’ and creates outsiders, but also abstracts a ‘‘majority will’’ out of a shared social situation. In this respect, the term ‘‘public’’ does not undo the specific set of social relations around ‘‘property’’ (or dispose the restrictions stemming from ownership) but delegates these relations to an abstract collective body.
Hardt’s and Roggero’s rejection of ‘‘public property’’ for the sake of a ‘‘communist project’’ brings the displacement of the term ‘‘public’’ from its hegemonic status of expressing an abstract collective will/body/thing. Therefore, the rejection of ‘‘public property’’ within the critique of political economy invites a novel political logic, which can now be conceived without having reference to the political terminology of liberal democracy. ‘‘Common’’ is not only ‘‘not property,’’ but it is also ‘‘not public’’; it signifies a collective social form that is different from the ‘‘public’’*/it doesn’t ‘‘substitute’’ the ‘‘public’’ but transcends it. Such a theoretical intervention allows us to speak a political language that is not structured with the binary opposition imposed by classical liberal and socialist discourses, and thus makes it possible for us to imagine a different form of ‘‘collectivity.’’ (http://dx.doi.org/10.1080/08935696.2010.490372)