Speculator

n. one who buys and sells commodities to profit from fluctuations in their market value, one who engages in any risky business venture in the hope of making large gains

Speculation, in the narrow sense of financial speculation, involves the buying, holding, selling, and short-selling of stocks, bonds, commodities, currencies, collectibles, real estate, derivatives, or any valuable financial instrument to profit from fluctuations in its price as opposed to buying it for use or for income via methods such as dividends or interest. Speculation or agiotage represents one of three market roles in Western financial markets, distinct from hedging, long- or short-term investing, and arbitrage.
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Noun
1. someone who makes conjectures without knowing the facts
(hypernym) thinker
(derivation) speculate
2. someone who risks losses for the possibility of considerable gains
(synonym) plunger
(hypernym) adventurer, venturer
(hyponym) hedger
(derivation) speculate, job

(n.)
One who speculates. Specifically: (a) An observer; a contemplator; hence, a spy; a watcher.
  

(n.)
One who forms theories; a theorist.
  

(n.)
One who engages in speculation; one who buys and sells goods, land, etc., with the expectation of deriving profit from fluctuations in price.
  

One, who attempts to anticipate price changes and, through buying and selling contracts, aims to make profits. A speculator does not use the market in connection with the production, processing, marketing or handling of a product. See: trader.