The glossary of the novel explains this as follows:
A death ritual that allows one who has lost honor to die well and go to Sto-Vo-Kor by being honorably killed by a House-mate or someone equally close.
Cite this entry
Definition of {ma'to'vor}
from the Klingon Language Wiki:
https://klingon.wiki/Word/Ma-to-vor
Retrieved 05 Feb 2023