The term UNPLEASANT SMELL can be described by several words, including REEK (4 letters), NIFF (4 letters), HUM (3 letters), STENCH (6 letters), ODOR (4 letters), MALODOR (7 letters), and STRONGODOR (10 letters). These words all refer to an unpleasant smell that is often described as pungent or acrid. REEK and STENCH are particularly strong words used to describe a very unpleasant smell, while NIFF and HUM are more subtle terms. ODOR and MALODOR are also used to describe an unpleasant smell, but they are not as strong as the other words. Finally, STRONGODOR is used to describe a particularly strong and unpleasant smell.