Britannica Dictionary definition of SHELF
[count]
1
:
a flat board which is attached to a wall, frame, etc., and on which objects can be placed
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Put the vase on the shelf.
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the top/bottom shelf of the kitchen cabinet
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Will you get that book down off the shelf?
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We don't have much shelf space.
—
see also bookshelf
2
geology
:
a flat area of rock, sand, etc., especially underwater
—
see also continental shelf
off the shelf
:
directly from a store without having to be specially made or ordered
on the shelf
:
in an inactive state
:
not active or being used