Congius

from WordNet (r) 3.0 (2006)

congius
    n 1: a British imperial capacity measure (liquid or dry) equal
         to 4 quarts or 4.545 liters [syn: {gallon}, {Imperial
         gallon}, {congius}]

from The Collaborative International Dictionary of English v.0.48

Congius \Con"gi*us\, n. [L.]
   1. (Roman Antiq.) A liquid measure containing about three
      quarts.
      [1913 Webster]

   2. (Med.) A gallon, or four quarts. [Often abbreviated to
      {cong.}]
      [1913 Webster]