What is the meaning of Magnum?

A bottle containing 1.5 liters of fluid, double the volume of a standard wine bottle.

A powerful firearm cartridge, often derived from a shorter, less powerful cartridge calibre that uses the same bullet.

A handgun that fires a cartridge of this calibre; chiefly a revolver, but rarely an autoloader firing an unusually powerful calibre.

magnum (bottle size)

Ellipsis of magnumpullo (bottle)

a bottle of wine containing 1.5 liters of fluid, double the volume of a standard bottle

inflection of magnus:

  1. nominative/accusative/vocative neuter singular
  2. accusative masculine singular

nominative/accusative/vocative neuter singular

accusative masculine singular

Source: wiktionary.org