1. not loyal or true to someone or something; breaking promises or commitments
2. having a romantic or sexual relationship with someone other than one’s spouse or partner
3. not accurate or true to an original

Examples

• The unfaithful servant betrayed his master’s trust.
• She discovered her husband had been unfaithful for years.
• The movie was unfaithful to the original book.
• His unfaithful friends abandoned him when he needed help most.
• The translation was unfaithful to the author’s intended meaning.
• Many considered him an unfaithful ally who couldn’t be trusted.
• The unfaithful adaptation changed too many important details.