Option block orders are large, privately negotiated orders. They're executed apart from the public auction market. 

Block trades were specifically designed for institutions and traders with major financial backing.

Here's a bit taken from Investopedia:

Due to the size of block trades, both on the debt and equities markets, individual investors rarely, if ever, make block trades. In practice, these trades typically occur when large hedge funds and institutional investors buy and sell large sums of bonds and shares in block trades via investment banks and other intermediaries.
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​http://www.investopedia.com/terms/b/blocktrade.asp
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