1) British capacity unit 2) Gallon 3) Imperial capacity unit 4) Imperial gallon 5) Unit of volume 
• (n.) A gallon, or four quarts. • (n.) A liquid measure containing about three quarts.
(from the article `measurement system`) ...and amphora for dry products and the quartarus, sextarius, congius, urna, and amphora for liquids. Since all of these were based on the ...
Con'gi·us noun [ Latin ] 1. (Roman Antiq.) A liquid measure containing about three quarts. 2. (Medicine) A gallon, or four quarts. [ Often abbreviated to cong. ]
(in prescriptions) a gallon (3.7853 liters). · an ancient Roman unit of liquid measure equal to about 0.8 U.S. gallon (3.2 liters).