bar.

1. 1. barometer
   2. barometric
2. barrel

The noun has 12 meanings:

Meaning #1: a room or establishment where alcoholic drinks are served over a counter
  Synonyms: barroom, saloon, ginmill, taproom

Meaning #2: a counter where you can obtain food or drink

Meaning #3: a rigid piece of metal or wood; usually used as a fastening or obstruction of weapon

Meaning #4: musical notation for a repeating pattern of musical beats
  Synonym: measure

Meaning #5: an obstruction (usually metal) placed at the top of a goal

Meaning #6: the act of preventing
  Synonym: prevention

Meaning #7: (meteorology) a unit of pressure equal to a million dynes per square centimeter

Meaning #8: a submerged (or partly submerged) ridge in a river or along a shore

Meaning #9: the body of individuals qualified to practice law in a particular jurisdiction
  Synonyms: legal profession, legal community

Meaning #10: a block of solid substance (such as soap or wax)
  Synonym: cake

Meaning #11: (British) a heating element in an electric fire

Meaning #12: (law) a railing that encloses the part of the courtroom where the judges and lawyers sit and the case is tried

The verb bar has 4 meanings:

Meaning #1: prevent from entering; keep out
  Synonyms: debar, exclude

Meaning #2: render unsuitable for passage
  Synonyms: barricade, block, blockade, block off, block up

Meaning #3: expel, as if by official decree
  Synonyms: banish, relegate

Meaning #4: secure with, or as if with, bars
  Antonym: unbar (meaning #1)