Nand[, , ... ] is the logical NAND function. It evaluates its arguments in order, giving True immediately if any of them are False, and False if they are all True.
Nand[, , ... ] can be input in StandardForm and InputForm as ... . The character can be entered as nand or \[Nand].
Nand[, , ... ] is equivalent to Not[And[, , ... ]].
Nand evaluates its arguments in a non-standard way (see Section A.4.2).
Nand gives symbolic results when necessary, removing initial arguments that are True.
Nand is not Flat.
See The Mathematica Book: Section 1.5.6.
See also: LogicalExpand, And.