An "immoral act" refers to a behavior or action that goes against accepted principles of right and wrong. It is something that is considered morally wrong or unethical. Full definition
It's sad that she thinks the only place to find morality is in a book just chock full of immoral acts. (religion.blogs.cnn.com)
Q: Can elected officials behave ethically and fulfill their public duties even if they have committed immoral acts in their personal life? (christianitytoday.com)
The two committed the same immoral act, yet one was lucky that no one was killed. (sciencedaily.com)