smell

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The sense, located in the nasal cavities of mammals and relying on the olfactory nerves, by which molecules borne in a fluid such as air can be perceived; the olfactory sense.
• noun A similar sense in other animals, as insects' ability to perceive air-borne molecules with their antennae.
• noun The act or an instance of smelling.
• noun A quality of something that is perceived by the sense of smell; an odor.
• noun A distinctive enveloping or characterizing quality; an aura or trace.
• intransitive verb To perceive (an odor) by the sense of smell.
• intransitive verb To perceive or detect (something) by a chemosensory organ, such as an antenna.
• intransitive verb To inhale the air near (something); sniff.
• intransitive verb To detect or discover, as by intuition or inference.
• intransitive verb To use the sense of smell.
• intransitive verb To sniff.
• intransitive verb To have or emit an odor.
• intransitive verb To have or emit an unpleasant odor; stink.
• intransitive verb To be suggestive; have a touch of something.
• intransitive verb To appear to be dishonest or corrupt.
• idiom (smell a rat) To suspect that something is wrong.
• idiom (smell blood) To sense an opportunity for advantage at someone else's expense.
• idiom (smell the roses) To spend time in leisurely enjoyment.

from The Century Dictionary.

• noun The faculty of perceiving by the nose; senseperception through the olfactory nerves; the olfactory faculty or function; the physiological process or function whereby certain odoriferous qualities of bodies, as scent or effluvium, are perceived and recognized through sensation; olfaction; scent; often with the definite article, as one of the special senses: as, the smell in dogs is keen.
• noun That quality of anything which is or may be smelled; an odoriferous effluvium; an odor or scent, whether agreeable or offensive; a fragrance, perfume, or stench; aroma: as, the smell of thyme; the smell of bilge-water.
• noun A faint impression; a subtle suggestion; a hint; a trace: as, the poem has a smell of the woods.
• noun An act of smelling: as, he took a smell at the bottle.
• To perceive through the nose, by means of the olfactory nerves; perceive the scent of; scent; nose.
• To perceive as if by smell; perceive in any way; especially, to detect by peculiar sagacity or a sort of instinct; smell out.
• To inhale the smell or odor of; test by the sense of smell: oftener intransitive, with of or at.
• To give out an odor; affect the olfactory sense: as, the rose smells sweet.
• Specifically, to give out an offensive odor: as, how the place smells!
• To have an odor (of a specified kind); be scented with: with of: as, to smell of roses.
• Figuratively, to appear to be of a certain nature or character, as indicated by the smell: generally followed by like or of.
• To inhale a smell or odor as a gratification or as a test of kind or quality, etc.: colloquially with of, formerly sometimes with to or unto.
• To snuff; try to smell something; figuratively, to try to smell out something: generally with about: as, to go smelling about.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb To affect the olfactory nerves; to have an odor or scent; -- often followed by of.
• intransitive verb To have a particular tincture or smack of any quality; to savor.
• intransitive verb To exercise the sense of smell.
• intransitive verb To exercise sagacity.
• transitive verb To perceive by the olfactory nerves, or organs of smell; to have a sensation of, excited through the nasal organs when affected by the appropriate materials or qualities; to obtain the scent of.
• transitive verb To detect or perceive, as if by the sense of smell; to scent out; -- often with out.
• transitive verb obsolete To give heed to.
• transitive verb [Colloq.] to have a sense of something wrong, not clearly evident; to have reason for suspicion.
• transitive verb [Colloq.] to find out by sagacity.
• noun (Physiol.) The sense or faculty by which certain qualities of bodies are perceived through the instrumentally of the olfactory nerves. See sense.
• noun The quality of any thing or substance, or emanation therefrom, which affects the olfactory organs; odor; scent; fragrance; perfume.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A sensation, pleasant or unpleasant, detected by inhaling air (or, the case of water-breathing animals, water) carrying airborne molecules of a substance.
• noun physiology The sense that detects odours.
• verb transitive To sense a smell or smells.