Definition of 'Manipulation'
The act of artificially inflating or deflating the price of a security. In most cases, manipulation is illegal. It is much easier to manipulate the share price of smaller companies, such as penny stocks, because they are not as closely watched by analysts as the medium- and large-sized firms.
Also known as "price manipulation."
Investopedia explains 'Manipulation'
One way people can deflate the price of a security is by placing hundreds of small orders at a significantly lower price than the one at which it has been trading. This gives investors the impression that there is something wrong with the company, so they sell, pushing the prices even lower. Another example of manipulation would be to place simultaneous buy and sell orders through different brokers that cancel each other out but give the perception, because of the higher volume, that there is increased interest in the security.