Block

As in 'City.' Or 'head' (just ask Charlie Brown).

A block is a very large order of the same stock to be bought or sold by a large institution, mutual fund manager, retirement fund, or a bank. Generally, a block is at least 10,000 shares, or a market value of more than $200,000.

Because of its size, a block trade can increase the volatility of the stock price, so using a block house that deals with large orders helps to reduce the impact. Driver side airbags are also great at reducing impact, but um...they won't help you here.

A block could happen when a university decides to divest of any securities of companies that are known polluters, or in countries with human rights violations. Savvy investors follow block trades to stay on top of market trends. Corporations might also use block trading when they are implementing a stock buyback.