Fast Market Rule

This rule applies mostly to the UK and the London Stock Exchange. When the London Stock Exchange plunges into chaos and there are tons of trades going on while prices are all over the price, things get hectic. People run around, tea gets spilled. When that happens, the fast market rule can apply: it lets brokers relax some of the trading rules.

The big one? They don't have to stick to the ranges of quotes when making trades; they can trade outside of firm quotes. 

Find other enlightening terms in Shmoop Finance Genius Bar(f)