on the shelf Definition

shelf
noun shelves

1. A usually narrow, flat board fixed to a wall or part of a cupboard, bookcase, etc, for storing or laying things on.

Thesaurus: counter, mantlepiece, rack.
2. Said especially of books: a shelf-ful.
3. A ledge of land, rock, etc; a sandbank.

Thesaurus: ledge, shoal, reef, ridge, sandbank, sandbar, terrace.

Idiom: on the shelf

Said of a person or thing: too old or worn out to be of any use.

Said of a person, especially a woman: no longer likely to have the opportunity to marry, especially because of being too old.

Etymology: Anglo-Saxon scylf.