Definitions of immoral:

• adjective:   violating principles of right and wrong
• adjective:   morally unprincipled

  Example: "Immoral behavior"

• adjective:   marked by immorality; deviating from what is considered right or proper or good
• adjective:   characterized by wickedness or immorality
• adjective:   not adhering to ethical or moral principles

  Example: "They considered colonialism immoral"