Not

Takes the two top values on the conditions stack and not's them. If both are true it will place a false on the conditions stack. If one is false or both are false it places a true on the conditions stack.

0 0 and puts 1 on the stack
1 0 and puts 1 on the stack
0 1 and puts 1 on the stack
1 1 and puts 0 on the stack

not results the exact opposite as and.