A liquid market refers to the market condition when there is a large number of buyers and sellers. This is when the market achieves a free-flowing state while allowing ease of trade at a lower cost.
The exact opposite of a liquid market is a thin market, where there is a huge discrepancy between the number of buyers and sellers. One of the most prominent examples is the New York Stock Exchange. Each day, millions of stocks are traded on large exchanges.
On the contrary, real estate can not be classified as a liquid market, given the limited number of buyers interested in getting their residential or commercial place. The transactions in such markets are often complicated as well.