What is moral turpitude?

From a legal standpoint, "moral turpitude" is defined as an act that grossly violates the standards of a community. This is mostly relevant because it can be used to deny access to, or deport, a person with immigrant status. It is not very specific, but crimes that fall under the rubric of "moral turpitude" might, according to the Immigration Legal Resource Center, include fraud, theft, or a variety of acts with "lewd intent." Because laws vary from state to state, one's immigration status after committing a crime can be fairly complex. Immigration judges are responsible for determining whether or not a specific crime involves moral turpitude. Additionally, there is a growing body of United States case law—but not federal statutory law—that affects these decisions. Generally speaking, conviction on two crimes involving moral turpitude triggers deportation for most immigrants.
https://www.ilrc.org/sites/default/files/resources/n.7-crimes_involving_moral_turpitude.pdf