Wash Trading

A process used by investors to manipulate prices on exchanges. The trader sells securities to himself (tokens or coins in a crypto exchange), therefore, making demand look bigger than it actually is and instantly inflating prices. They usually require a buyer and a colluding broker who is part of the trade, but in the cryptocurrency world the trader might have two different anonymous addresses which he controls and he can just make the trade flow from one address to another.

It is illegal in the US and the IRS bars taxpayers from deducting losses that result from wash trades.