Look up: Shell-keep

1. Shell Keep
   A shell keep was a stone walled enclosure built around the top of a motte. A shell keep is relatively small, probably between 15m and 25m diameter, usually circular with few buildings, and perhaps one tower only, within its interior. Shell keeps could be defended habitations, or military strongholds...
   Found on http://www.keystothepast.info/durhamcc/k
   
   
2. Shell Keep
   Castle consisting of a high strong ring wall with residential buildings on its inner face. Examples: Clifford's Tower - York, Arundel Castle
   Found on http://www.encyclo.co.uk/visitor-contrib
   
   
3. Shell keep
   A `shell keep` is a style of medieval fortification, best described as a stone structure circling the top of a motte. In English castle morphology, shell keeps are perceived as the successors to motte-and-bailey castles, with the wooden fence around the top of the motte replaced by a stone wall. Cas...
   Found on http://en.wikipedia.org/wiki/Shell_keep
   
   
4. Shell-keep
   Circular or oval wall surrounding inner portion of castle; usually stores and accommodations inside the hollow walls.
   Found on http://www.encyclo.co.uk/local/20018
   
   
5. Shell-keep
   round wall, usually built on top of a motte, in which the castle buildings are built up against the inner wall forming a circular courtyard
   Found on http://www.castlexplorer.co.uk/glossary.