Definitions:

1. having sexual relations with someone other than your husband or wife, or your boyfriend or girlfriend adjective
   • Their spouse was unfaithful.
2. not true to duty or obligation or promises adjective
   • an unfaithful lover
3. not trustworthy adjective
   • an unfaithful reproduction

Synonyms:

• faithless
• traitorous
• treasonable
• treasonous

NearBy Words:

• unfaithfully
• unfaithfulness