This term has a number of potential meanings:
In the context of acquisitions, the process of the seller making general and specific disclosures against the warranties (www.practicallaw.com/A37201) contained in an acquisition (www.practicallaw.com/A34565) agreement. If the seller fails to disclose a relevant matter, in respect of the warranties, it may be sued by the buyer for breach of warranty. The seller usually makes his disclosures in a disclosure letter (www.practicallaw.com/A34883) and attaches relevant documents to that letter to support its disclosures.
In the context of civil litigation, stating, usually in a formal list (www.practicallaw.com/7-205-6237), whether a document exists or has existed and whether you are willing to allow your opponent(s) to inspect it. For more information on the disclosure process, see Practice notes, Disclosure: what is it and where are the rules? (www.practicallaw.com/6-203-8753) and Disclosure: an overview (www.practicallaw.com/5-203-8758).