dropwall

noun3

1. •
   A short wall used as a weir or floodgate to control the flow of water.

   • The entire work, with the exception of the upper six feet of the weir dropwall and the superstructure of the head-lock, has been completed — 1867
2. •
   A prefabricated wall that is supported by a framework.

   • In the new mood of economy, it received a dropwall tripling rather than the thorough makeover of Leeds, Glasgow and Manchester. — 2002
3. •
   A temporary barrier used to surround troops or protect battlements, often with spikes on the outside to prevent the enemy from scaling it.

   • A dropwall took a direct hit and shuddered. — 2020