1. In mathematics and in programming and computer applications, a symbol or other character indicating an operation that acts on one or more elements. See also binary, unary.
2. A person who controls a machine or system such as a computer or telephone switchboard.

ETYM Latin.
1. An agent that operates some apparatus or machine; SYN. manipulator.
2. Someone who owns or operates a business.
3. Someone who handles telephone inquiries and helps callers to make connections.
4. A speculator who trades aggressively on stock or commodity markets.
5. (Mathematics) A symbol that represents a function from functions to functions.