a thin slab of wood, metal, etc., fixed horizontally to a wall or in a frame, for supporting objects.

the contents of this

a shelf of books.

a surface or projection resembling this; ledge.

Physical Geography .

a sandbank or submerged extent of rock in the sea or river.

the bedrock underlying an alluvial deposit or the like.

continental shelf.

Archery . the upper part of the bow hand, on which the arrow rests. ?

off the shelf

readily available from merchandise in stock

Any of those parts can be purchased off the shelf.

on the shelf

Informal .

put aside temporarily; postponed.

inactive; useless.

without prospects of marriage, as after having broken an engagement.

noun

bank , bracket , console , counter , cupboard , ledge , mantelpiece , mantle , rack , reef , ridge , rock , shallow , shoal , banquette , bedrock , jutting , layer , mantel , sandbank , sandbar , sill , slab , stratum