What is NOR logical operator?

Question

Is nor:

!(a or b)
!a or !b
!(a and b)

something else?

Answer 1

!(a or b)

see http://en.wikipedia.org/wiki/Logical_NOR for more:

In boolean logic, logical nor or joint denial is a truth-functional operator which produces a result that is the negation of logical or. That is, a sentence of the form (p NOR q) is true precisely when neither p nor q is true—i.e. when both of p and q are false. In grammar, nor is a coordinating conjunction...

Answer 2

!(a or b)