noun

1. a person who operates; specif.,
   1. a person who effects something; agent
   2. ☆ a person whose work is operating a machine; specif., a person who operates a telephone switchboard a telephone operator
   3. ☆ a person engaged in financial, commercial, or industrial operations; owner or manager of a mine, railroad, factory, etc.
2. ☆ Slang a clever, persuasive person who generally manages to achieve his or her ends
3. Math. any symbol or term conventionally indicating that a certain process, substitution, etc. is to be carried out