Iron-hearted is a term used to describe someone who is largely unemotional, tough, and unsympathetic. Synonyms for this term are often found in words that share similar characteristics. Some common synonyms for iron-hearted include unfeeling, cold-hearted, callous, stony, and unemotional. Other synonyms that can be used in different contexts are uncompassionate, heartless, unyielding, hard-hearted, and tough-minded. Each of these words describes a similar but slightly different aspect of the trait being referred to. Ultimately, all these synonyms describe a lack of empathy or sentimentality, and each one can be used to effectively convey the same meaning as iron-hearted.