Something that gives up an asset, potential asset, right(s) or potential right(s). In the context of intellectual property, it means the right-holder giving up rights they otherwise could have asserted, which could be some or all of the rights associated with the intellectual property, or some of the term of the IP. See Terminal Disclaimer, Prosecution Disclaimer, Release [of Claims]
With respect to torts and other claims, general blanket liability disclaimers (all risks) are very hard to enforce – disclaimers with respect to a specific identified risk associated with a voluntary activity are much more enforceable, absent gross negligence – but the party claiming the benefit of the disclaimer usually has to show “privity of contract” between the it and the injured party – which is where a lot of disclaimers fall apart. Moreover, usually on public policy grounds, disclaimers usually will not protect against gross and/or wilful negligence or accidents which result from breaches of laws, regulations and safety codes – since this is seen as potentially encouraging undue risk taking and the risk of creating public charges.