A brokerage firm that trades against its own customers by entering orders opposite to those entered by its customer without actually executing the clients' orders on the global interbank currency exchange market.

A price movement pattern characterized by a moderate (and ungrounded) rise in the price of a stock followed by a spectacular fall. It is derived from the expression "even a dead cat will bounce if it falls from a great height".

http://en.wikipedia.org/wiki/Dead_cat_bounce

Note: Not sure if applicable to Forex? Comments, anyone?

ECN is an acronym for Electronic Communications Network. A Forex ECN Broker does not operate a dealing desk and thus does not take counterpart positions against their clients but instead provides a marketplace where multiple market makers, banks and retail traders can enter competing bids and offers into the platform either inside or outside the spread, allowing all parties to trade against each other and with multiple counterparties. A trader might open a trade with liquidity provider "A" and close it with liquidity provider "B", or have the trade executed against the bid or offer of another trader. Participants of the ECN send in competing bids and offers into the platform and the combined volume is usually displayed to traders at each price. Orders are matched between counterparties.

Typically ECN brokers charge a small commission for their services (on top of the spread, which is normally very low). This commission is the price that the parties pay for having access to a completely "fair" trading environment.

ECN Brokers and NDD ("No-Dealing-Desk") Brokers are aften used as synonyms but are not exactly the same. Examples of ECN brokers are MB Trading and  Hotspot FX