From Computer History Wiki
The term 'operator is sometimes used to refer to a computer operator.
In programming languages, an operator is a directive which works on one or two (usually) data values(s), the operands, in some way; thereby producing another value, which is then used in some way - perhaps as part of a larger expression in the program.
Operators which take a single data item are sometimes called 'unary', and those which take two can be called 'binary'.
An example of unary operator would be a bit-wise inversion, and binary operators include the usual arithmetic operations +, /, etc.