bell jar

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A cylindrical glass vessel with a rounded top and an open base, used to protect and display fragile objects or to establish a vacuum or a controlled atmosphere in scientific experiments.

Century Dictionary and Cyclopedia

1. n. A bell-shaped glass jar, used by chemists, in physical laboratories, etc., for receiving a gas lighter than the atmosphere or other medium in which it is plunged, and for similar uses. It is a form of bell-glass.

Wiktionary

1. n. A piece of laboratory equipment used for creating vacuums, often made of glass in a bell-like shape.

GNU Webster's 1913

1. (Phys.) A glass vessel, varying in size, open at the bottom and closed at the top like a bell, and having a knob or handle at the top for lifting it. It is used for a great variety of purposes; as, with the air pump, and for holding gases, also for keeping the dust from articles exposed to view.
2. n. See in the Vocabulary.

WordNet 3.0

1. n. a bell-shaped glass cover used to protect and display delicate objects or to cover scientific apparatus or to contain gases