(Don't Know) Indicates refusal of payment or delivery on a transaction because the trade or some of its details are not known or there is an error or disagreement as to the agreed terms
A designation (derived from an abbreviation of the words "don't know") indicating that a party does not have a record of a transaction another party is confirming to him or has no instructions or records indicating that he should accept a delivery being tendered to him
A securities term used to denote a trade which is rejected back to the originating broker