can·is·ter 
(kănĭ-stər)
(kănĭ-stər)n.
1. A usually cylindrical storage container, especially:
a. A box or can of thin metal or plastic used for holding dry foodstuffs or cooking ingredients, such as flour or sugar.
b. A small plastic container used for storing a roll of film.
c. A metal container that holds pressurized gas, as one containing tear gas that explodes on impact or one containing oxygen as part of a breathing apparatus.
2.
a. A metallic cylinder packed with shot that scatter upon discharge from a cannon, formerly used as an antipersonnel round.
b. Such cylinders, or the shot used in such cylinders, considered as a group.
3. The part of a gas mask that contains the filter for removing toxic agents from the air.
[Latin canistrum, basket, from Greek kanastron, from kanna, reed; see CANE.]