A glass jar or bottle used to accumulate electricity. It is coated with tin foil, within and without, nearly to its top, and is surmounted by a brass knob which communicates with the inner coating, for the purpose of charging it with electricity. It is so named from having been invented in Leyden, Holland.
  

The following video provides you with the correct English pronunciation of the word "leyden phial", to help you become a better English speaker.