A logical bitwise operator. NOR is a binary operator meaning it takes two inputs. The symbol for a NOR gate is the same as an OR gate with a dot a the front for negation.
The gate looks like this
\-\
A---\ \
| |0----Result
B---/ /
/-/
The truth table is below.
A B Result
1 1 0
1 0 0
0 1 0
0 0 1