The latest bid (buy) and ask (sell) price available for a security.
Example: A stock quoted at $49.95 / $50.00 means the highest buyer is willing to pay $49.95, and the lowest seller is offering at $50.00.
A high-frequency trading tactic involving rapidly placing and canceling large numbers of orders to confuse or slow down other traders' systems.
Intent: Create false impressions of market activity or cause delays.
Status: Considered manipulative and banned in many jurisdictions.