A pocket listing is a home for sale by a Realtor which has not been placed in the MLS, or "on the open market". It is called a pocket listing because the listing agent (who represents the seller) does not widely market the home, keeping it in his or her "pocket", as requested by the seller.
Why might a seller not choose to market their home via the MLS? Though it's THE marketplace for homebuyers and where all the action is, sometimes