Definitions:

1. not to be placated or appeased or moved by entreaty adjective
   • grim determination

Synonyms:

• black
• dark
• forbidding
• ghastly
• inexorable
• low
• relentless
• stern
• unappeasable
• unforgiving
• unrelenting

NearBy Words:

• grimace
• grime
• griminess
• grimly
• grimm
• grimness
• grimoire
• grimy