See
Multiprocessing - Wikipedia. It (currently) defines multiprocessing as "the use of two or more central processing units (CPUs)". However I am nearly certain that the term is also used to refer to multiple processes in a single processor. It is not worthwhile updating the article without an authority so if someone has something authoritive with the alternative definition then that would help. The Wikipedia is supposed to explain the way things are and not alter things in some way that people think things should be so it would help to improve the understanding of what multiprocessing is.