1. 1. A flat, usually rectangular structure composed of a rigid material, such as wood, glass, or metal, fixed at right angles to a wall or other vertical surface and used to hold or store objects.
   2. The contents or capacity of such a structure.
   3. Something, such as a projecting ledge of rock or a balcony, that resembles such a structure.
2. A reef, sandbar, or shoal.
3. Bedrock.

off the shelf

1. From ready-made merchandise in stock: supplies that were available off the shelf.

1. In a state of disuse.
2. 1. Unemployed.
   1. Out of circulation.
   1. Retired.

[Middle English, probably from Middle Low German schelf.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.