bell jar

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun 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.

from The Century Dictionary.

• noun 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.

from the GNU version of the Collaborative International Dictionary of English.

• (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

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

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a bell-shaped glass cover used to protect and display delicate objects or to cover scientific apparatus or to contain gases