in•fi•del•i•ty Pronunciation: (in"fi-del'i-tE) —n., —pl. -ties. 1. marital disloyalty; adultery. 2. unfaithfulness; disloyalty. 3. lack of religious faith, esp. Christian faith. 4. a breach of trust or a disloyal act; transgression. More than one hundred million people in the United States alone, are affected by infidelity. Peter touches on the subject in the Slow, Deep, and Hard release.