1) A market which only can quote a firm price on either the bid or the ask side. This can be caused by temporary market inefficiencies or by regulatory controls, as can be found in some foreign countries. A one-way market also can be created when there are only buyers, or only sellers, interested in a particular asset or security at a specific point in time.
2) A slang term to describe a market that is moving strongly in one direction with little resistance.
Taobiz explains One-Way Market
1) Certain countries have created one-way markets for themselves in respect to foreign investment - in Korea, for instance, investors typically can purchase only initial public offerings of companies, and no investing is allowed on the secondary markets once that window has passed.
2) A good example of a one-way market would be the ending stage of the technology-driven bull market of the late 1990s. In January of 2000, nearly every stock was rising every day, regardless of the fundamentals at the time.