/in'fi del"i tee/ , n. , pl. infidelities .
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.
[ 1375-1425; late ME infidelitas, equiv. to infideli ( s ) unfaithful (see INFIDEL) + -tas -TY 2 ]