The word flinthearted is often used to describe individuals who lack compassion and empathy towards others. Synonyms for this term include callous, unfeeling, heartless, hard-hearted, and cold-blooded. Other synonyms for flinthearted may include unkind, indifferent, unsympathetic, ruthless, and cruel. Each of these terms refers to a person who is lacking in the ability to feel for others and show kindness and understanding. These words can be used to describe anyone from a cold-hearted boss to a heartless criminal. Regardless of the context, flinthearted synonyms suggest a total lack of empathy towards others and the potential for extreme uncaring behavior.