Simple Definition:

Iniquities are unjust [not fair] or immoral [not conforming to accepted standards of morality] acts or behaviors. They refer to actions that are considered to be sinful, wicked, or morally wrong. Examples of iniquities include stealing, lying, or cheating

Very Simple Definition:

Iniquities are actions that are very bad or wrong. They are things that people should not do. Examples of iniquities are stealing, lying, or cheating.