a person who operates a machine, apparatus, or the like

a telegraph operator.

a person who operates a telephone switchboard, esp. for a telephone company.

a person who manages a working or industrial establishment, enterprise, or system

the operators of a mine.

a person who trades in securities, esp. speculatively or on a large scale.

a person who performs a surgical operation; a surgeon.

Mathematics .

a symbol for expressing a mathematical operation.

a function, esp. one transforming a function, set, etc., into another

a differential operator.

Informal .

a person who accomplishes his or her purposes by devious means; faker; fraud.

a person who is adroit at overcoming, avoiding, or evading difficulties, regulations, or restrictions.

a person who is extremely successful with or smoothly persuasive to members of the opposite sex.

Genetics . a segment of DNA that interacts with a regulatory molecule, preventing transcription of the adjacent region.

noun

motorist , adventurer , gambler , agent , broker , computer , conductor , dealer , driver , emergency , manager , speculator , switchboard , telephone , user