Definition of market abuse

This category of securities law violations can cover a wide range of bad behaviour.  One of the most common violations is insider trading or also known as insider dealing, which is defined in the UK as selling or buying securities, such as shares or bonds, based on non-public market moving information.

The US definition is somewhat tighter, because the courts require the information to be used in violation of a duty to keep it quiet.

Example
The other main form is market manipulation, which includes lying about a company to drive its share price down and "pump and dump" schemes, in which holders of a security improperly talk it up until the price rises and then sell it to unwitting investors.

The US is historically the most vigorous prosecutor of market abuse cases but both Hong Kong and the UK have stepped up enforcement.  [1]