cell wall

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

• noun The rigid outermost cell layer found in plants and certain algae, bacteria, and fungi but absent from animal cells.

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

• noun cytology A thick, fairly rigid, layer formed around individual cells of bacteria, Archaea, fungi, plants, and algae (but not animals and other protists which generally have cell membranes without cell walls). The cell wall is external to the cell membrane and serves a structural function helping the cell maintain its shape and protecting the cell from damage.

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

• noun a rigid layer of polysaccharides enclosing the membrane of plant and prokaryotic cells; maintains the shape of the cell and serves as a protective barrier