Rest or repose; peaceful rest (can be used in a religious or literary sense, e.g. eternal rest).
彼は長年の闘病の末、ついに安息を得た。
After years of illness, he finally found rest.
日曜日は家族と過ごし、心身ともに安息を取る。
On Sundays I spend time with my family and get physical and mental rest.
墓地で祖父のために安息を祈った。
At the cemetery I prayed for my grandfather's repose.