General Synonyms:
* Disloyal: This is a common synonym that emphasizes a lack of commitment or allegiance.
* Treacherous: This implies a betrayal of trust, often with malicious intent.
* Faithless: This is a direct synonym that emphasizes a lack of belief or trust.
* Untrustworthy: This suggests that someone is unreliable and cannot be depended upon.
* Deceitful: This emphasizes the act of misleading or lying.
* Two-faced: This suggests someone who is hypocritical and says one thing but does another.
More Specific Synonyms:
* Adulterous: This refers specifically to infidelity in a romantic relationship.
* Perfidious: This implies a betrayal of trust with malicious intent, often involving a breach of loyalty.
* Duplicitous: This suggests someone who is deliberately deceitful and misleading.
* Inconstant: This emphasizes a lack of steadiness or consistency, particularly in relationships.
* Reneging: This refers to breaking a promise or agreement.
The best synonym to use will depend on the specific context and the nuance you want to convey.