Co-processor
From Computer History Wiki
A co-processor is a block of logic forming a complete data processing unit attached to a CPU, which operates in tandem with the main CPU, under its direction, to perform some of the processing functions of the system.
Floating point units are often co-processors (e.g. the FP11 floating point units of many PDP-11s); channels are effectively co-processors which are specialized to doing I/O.
