preassembled

adjective

pre·​as·​sem·​bled ˌprē-ə-ˈsem-bəld 

variants or pre-assembled

: having been assembled in advance

… if your walls, floor and ceiling are irregular, a preassembled wall may not fit properly without a lot of shimming and adjusting.

—A. J. Hand

preassembly

ˌprē-ə-ˈsem-blē 

noun

or pre-assembly

plural preassemblies or pre-assemblies

A key goal of the new factory is to give the company more space to do preassembly of equipment …

—Steve Toloken

Word History

First Known Use

1939, in the meaning defined above