Definitions
1.nounThe act of negating something.
2.nounA denial or contradiction.
3.nounA proposition which is the contradictory of another proposition and which can be obtained from that other proposition by the appropriately placed addition/insertion of the word "not". (Or, in symbolic logic, by prepending that proposition with the symbol for the logical operator "not".)
4.nounThe logical operation which obtains such (negated) propositions.