On February 4, the Securities and Exchange Commission approved a rule proposed by the CBOE Stock Exchange (CBSX) to adopt a Trade, Flash and Cancel order type. Such orders will be executed against the quotation published on the CBSX automatically if the CBSX is quoting at the national best bid or offer (NBBO) when the order is submitted. However, if the CBSX is not quoting at the NBBO, then a Trade, Flash and Cancel order will be electronically exposed to CBSX traders for up to three seconds, rather than being routed to other markets, to provide CBSX traders the opportunity to trade with the order by matching or improving the NBBO. Use of the Trade, Flash and Cancel order type is voluntary.  

http://www.sec.gov/rules/sro/cboe/2009/34-59359.pdf