1.NounA mechanical or electronic device that performs mathematical calculations; an electronic one specifically.
"electronic calculator; pocket calculator; The calculator on a bookkeeper's desk in the 1950s was an adding machine with mechanical guts.; I told him to hand me a calculator and he jokingly placed an adding machine at my side."
2.NounA person who performs mathematical calculation.
"During the war, his grandmother had worked at the Bletchley Park decoding station as a calculator."
3.NounA person who calculates (in the sense of scheming).
"He revealed himself to be a cold-blooded calculator out to sabotage his colleagues."