Meaning : Not to be placated or appeased or moved by entreaty.
Example :
Grim determination.
Grim necessity.
Russia's final hour, it seemed, approached with inexorable certainty.
Relentless persecution.
The stern demands of parenthood.
Synonyms : grim, inexorable, stern, unappeasable, unforgiving, unrelenting
Meaning : Never-ceasing.
Example :
The relentless beat of the drums.
Synonyms : persistent, unrelenting