What does "peace of mind" mean?

The absence of mental turmoil or anxiety.

Peace of mind

Common synonyms include: acceptance, ataraxia, ataraxis, buddha-like composure, calm disposition, calm of mind.

noun

noun ·Uncommon ·Advanced level

Noun

1
The absence of mental turmoil or anxiety. uncountable
"These people are under continual disquietudes, never enjoying a minute's peace of mind."
2
the absence of mental stress or anxiety wordnet

"These people are under continual disquietudes, never enjoying a minute's peace of mind."