Smell: The sense that provides information about an object's scent, often giving clues to the palatability of food, the safety of air, and other matters. The organs of smell are made up of patches of tissue called the olfactory membranes that are each about the size of a postage stamp. These membranes are located in a pair of clefts just under the bridge of the nose. Most air breathed in normally flows through the nose, but only a small part reaches the olfactory clefts'just enough to get a response to an odor. When a person sniffs to detect a smell, air moves faster through the nose, increasing the flow to the olfactory clefts and carrying more odor to these sensory organs.