Dictionary.net

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

One who forms theories; a theorist.

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 speculates.

n. One who speculates or forms theories ; an observer ;-one who buys goods, land, or other things, with the expectation of a rise of price, and of deriving profit from such advance.