nutshell

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

• noun The shell enclosing the meat of a nut.
• idiom (in a nutshell) In a few words; concisely.

from The Century Dictionary.

• noun The hard shell which forms the covering of the kernel of a nut: used proverbially for anything of small content or of little value.
• noun A bivalve mollusk of the family Nuculidæ; a nutlet.

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

• noun The shell or hard external covering in which the kernel of a nut is inclosed.
• noun Hence, a thing of little compass, or of little value.
• noun (Zoöl.) A shell of the genus Nucula.
• noun in a summarized and very abbreviated form; -- of statments, descriptions, reports, and other communications.
• noun to be within a small compass; to admit of very brief or simple determination or statement.

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

• noun The shell that surrounds the kernel of a nut.
• noun A short book summarizing an area of law.
• verb transitive To summarize (from the term in a nutshell).

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

• noun the shell around the kernel of a nut