From Longman Business Dictionary
speculatorspec·u·la·tor /ˈspekjəleɪtə-ər/ noun [countableC]FINANCE someone who buys goods, shares, property, or foreign currency in the hope that their value will increase so that they can be sold again at a higher price in order to make a profitSpeculators who bought the options before the bid and sold 24 hours later showed a 100% profit.
a currency speculator
a Wall Street speculator