It most likely means that the owner is going through the foreclosure process. This can easily be ascertained through a search of the public record. Any agent can help you with this information. In the current market, there is no single way to describe the foreclosure process, but I will give you general information.
If a homeowner falls behind on their payments, the bank can record a document and post the property with a copy of that document called "A Notice of Default". This tells the "world" that the borrower (owner) is in default. The recordation starts the clock on the process. The borrower has 90 days to bring the loan current by paying all unpaid principle, interest and any fees for the foreclosure costs to date. If not brough current, the lender can record a "Notice of Trustee Sale". This notice is also posted on the property and recorded and sets the date and time the property will be "sold" at the foreclosure acution, typically held at the county courthouse. A complete explanation of the foreclosure process, postponements, minimum bids and timing is very involved and would take a lot of time to explain but I won't go into that since that is not your question.
Suffice to say that if an owner is going through that process, they might be trying to sell the home on a "short sale". Banks have different departments doing different things, some simultaneously. For example a foreclosure process can continue while the short sale department is reviewing a short sale request from the borrower. At the same time, the collection department is calling to seek payment. All are independent departments. If a short sale is accepted and approved by the bank before the foreclosure sale takes place, the property is sold by the owner to another party and "beats" the foreclosure sale. A short sale simply means the home is sold "short" of what is owed to the bank.