Speculator

Part of speech: noun (n.)

1. One who speculates. Specifically: (a) An observer; a contemplator; hence, a spy; a watcher. [Obs.] Sir T. Browne.

2. One who forms theories; a theorist. A speculator who had dared to affirm that the human soul is by nature mortal. Macaulay.

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