An acceleration in an instrument's price. Traders will then often take a long or short position in the instrument with the hope that its momentum will continue in either an upward or downward direction. This strategy relies more on short-term movements in price rather than fundamentals.
With reference to: Momentum Traders | Investopedia http://www.investopedia.com/universi...#ixzz3yoBhfBfN
See also: https://en.wikipedia.org/wiki/Momentum_trader