shelf1
  
  n.
 (pl. shelves)
  - a flat length of wood or rigid material attached to a wall or forming part of a piece of furniture, providing a surface for the storage or display of objects.
 - a ledge of rock or protruding strip of land. 
▸a submarine bank, or a part of the continental shelf.
 
 
  Phrase
  
    - off the shelf
 not designed or made to order.  - on the shelf
  - no longer useful or desirable.
 - past an age when one might expect to be married.
 
 
   
  Derivative
  
    - shelf-ful n. 
(pl. shelf-fuls)
.  - shelf-like adj.
 
   
  Etymology
  ME: from Mid. Low Ger. schelf; rel. to OE scylfe ‘partition’, scylf ‘crag’.
 
  
    
shelf2
  
  n.
 (pl. shelfs)
 an informer.
v.
 inform on.
 
  Etymology
  1930s: prob. from the phr. on the shelf ‘out of the way’.