How exactly does the Constitution of India define 'Property'?
The short answer is that it doesn't.
This definition has been left to the courts of India that are forced to interpret the Constitution of India to determine based upon the intent of the drafters of the Constitution of India and the legal meaning of the word at the time it was adopted, on a case by case basis as issues are presented to it in real world cases.
There is, of course, lots of case law interpreting the Constitution of India, and a copy of it annotated with the decisions interpreting the various provisions related to Property would provide insight.
I recognize that the content of those decisions is probably what you really meant to ask about, but I don't have access to legal resources that can answer the obvious follow up question to my answer. A short law student note in an Indian law review indicates that almost every aspect of this definition is highly contentious and the subject of ongoing constitutional litigation:
In terms of its existence and construction, right to property is
perhaps the most contentious human right. The debate centres on who is
considered to have property rights protected, what types of property
are protected, why property can be regulated and the amount to which
property is protected is limited under all human rights documents,
either implicitly or explicitly. This paper analyses the continued
efforts of the Indian State to reshape ownership relations in society,
in order to achieve the aims of economic development and social
development, as seen from drafting the original clause on
constitutional ownership and its development through judicial
interpretation, legislation and the constitutional amendment, with
Article 300A being the focal point.
A 2010 article on point states:
The obvious first question is as to whether or not ‘intellectual
property’ such as ‘clinical trial data’ would fall within the
definition of ‘property’ as understood in Article 300A. There seems to
be enough authority to support the proposition that ‘property’ as
understood in Article 300A is wider than just ‘immovable property’.
One such authority in the context of ‘intellectual property rights’ is
the judgment of the Supreme Court in the case of Entertainment Network
India Ltd. (ENIL) v. Super Cassette Industries Ltd. (SCIL). In
pertinent part the Court held the following:
The ownership of any copyright like ownership of any other property
must be considered having regard to the principles contained in
Article 19(1)(g) read with Article 300A of the Constitution, besides,
the human rights on property.
The judgment goes on further to say that:
But the right of property is no longer a fundamental right. It will be
subject to reasonable restrictions. In terms of Article 300A of the
Constitution, it may be subject to the conditions laid down therein,
namely, it may be wholly or in part acquired in public interest and on
payment of reasonable compensation.
The fact that the Supreme Court recognizes ‘copyright’ to fall within
Article 300A is indicative that even ‘clinical trial data’, collected
after extensive experimenting, should in all likelihood fall within
the definition of ‘property’ as understood in Article 300A.
Given that article, the answer to this question:
can [intellectual property] be ultimately be forcefully acquired by
the State, if purpose is 'public welfare' and reasonable compensation
is provided?
appears to be that, yes, it can be.