market maker

1. One (as a person or firm) that, on a continuous basis, buys and sells a security for one's own account. Market makers usually try to profit from a rapid turnover in security positions rather than from holding those positions in anticipation of gradual price movements. Dealers in the over-the-counter market are market makers. See also make a market.
2. A dealer in options on the floor of an options exchange who makes a market in one or more options. The Chicago Board Options Exchange uses market makers.