One who was guilty of accidental homicide, and was entitled to flee to a city of refuge (Numbers 35:6,12,22,23), his compulsory residence in which terminated with the death of the high priest. (See CITY OF REFUGE .)
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain, copy freely.
Easton, Matthew George. "Entry for 'Manslayer'". "Easton's Bible Dictionary".